While the Sims is loading, messages run across a splash screen which is different for each expansion pack. This splash screen can be replaced with something else. (As can the messages, see Strings to tinker with.) There are sites with replacement splash screens, one of them reading "Superstar - Bugs Galore" which, for its submenu and teleporter problems, this EP fully deserved.
While the Sims is running, when not playing with or creating a family, the game shows the neighbourhood screen. This screen, too, can be replaced with something else. A paysite had differently themed neighbourhood screens. The game itself comes with standard "US" and "non-US" screens (one has a wide tarmac road, the other a grey road with sidewalks). The same applies to the Downtown, Vacation Island, Studio Town and Magic Town screens.
In fact, all the game graphics that are not object graphics or textured meshes can be customized. That is: all the bars and buttons that can show at the bottom of the screen while playing a family, the bar and buttons above the neighbourhood/other-lot screens (and of course the screens themselves) and every component of the Create-a-Sim screen.
I've seen a forum post on how to replace the default neighbourhood screen, but it wasn't very detailed, and said nothing about other replacable components. On yet another forum was mentioned a site with replacement buttons edited to look as if they were made out of wood; sadly, that site had closed. So it seems worthwhile to write a little DIY howto on the subject.
The graphics in question can be found in "UIGraphics.far" in the subdirectory UIGraphics. Replacing any of them works in the same way as replacing any Sims default: simply put a file with the same name in the directory that the FAR file is in, and the game loads that file instead. Don't forget, though, to duplicate the FAR file's internal directory structure as well as the file to replace. So, to have the game show a custom bulldozer button for the Downtown screen, make a new bitmap called "Bulldoze.bmp" (the same size as the old one, of course) and a subdirectory UIGraphics\Downtown to put it in.
File Archive Reader II (and probably most FAR readers) allows me to see the subdirectories inside "UIGraphics.far". This file contains a huge number of BMPs, a number of CUR and FNT files (even Russian, and that while the game reserved a language slot for Russian but didn't implement it) and the odd other format. Most of the file and directory names are self-explanatory, but the best thing to do when making a replacement is to unarchive the whole FAR to somewhere on disk and then browse the images. The directories cpanel and NghUi contain graphics for respectively the control panel (visible when playing with a family) and the neighbourhood bar; more graphics can be found in Shared, although I'm not sure all of them are used in the game. The directories Downtown, VIsland, StudioTown and MagicTown contain graphics specific to those locations: mainly, the town screens and the taxi/boat/etc. screen displayed while that location is being loaded. Community is a special case as it is both visitable and the main neighbourhood; so this is where the new neighbourhood screen can be found. The old ten-lot neighbourhood screen and all the buttons for creating Sims and extras (like the Spellbook selection graphics, and the pictures displayed as Townies, Studio extras etc. are being created) are found in the old neighbourhood directory, Nhbd. Other contains, most importantly, the splash screens, all misleadingly called "[language]setup.bmp".
So, how to go about replacing the default bitmaps? (I suppose it would also be possible to replace the default fonts and cursors, but that's taking customization very far!) The buttons andsuch are easiest: simply edit and put in the right directory. They are scattered over three directories, however, and changing one item means also having to change whatever other item is used with it. For instance, colorizing the general buttons from Shared\Sys pink means also finding and colourizing all backgrounds these buttons may be used against. The "transparent" areas of all bmps - the parts where the background shines through - are generally violet, and should not be altered or smoothed through anti-aliasing. The easy thing about these components is that you don't have to worry about what name to give them; the old name will do.
Neighbourhood screens follow this pattern: a main background screen and "animation" bitmaps (with plenty of transparent violet) consecutively mapped against the main background for an illusion of motion. These are generally of water, but the Community screen has a rising and sinking Nessie, while Magic Town has its balloon. (There may be extra files overlaying the background, like the neighbourhood signboard and the dock on Vacation Island; this differs per hood). Again, the transparent areas must not be changed in any way (unless you know exactly what you're doing). The main screen is called "Nscreen.bmp" or "Dscreen.bmp" or whatever, and the animation screens have the same name followed by the numbers of their order of appearance, and possibly an extra tag. For instance, the Downtown screens are called:
dscreen.bmp dscreen01.bmp dscreen02.bmp dscreen03.bmp dscreen04.bmp dscreen05.bmp
While the Community screens are called:
NScreen_unleashed.bmp NScreen_unleashed_waves001.bmp NScreen_unleashed_waves002.bmp NScreen_unleashed_waves003.bmp NScreen_unleashed_waves004.bmp NScreen_unleashed_waves005.bmp NScreen_unleashed_waves006.bmp ness01.bmp ness02.bmp ness03.bmp
And all Community screens starting with "Nscreen" also have a "non-US" variant. In the old ten-lot neighbourhood screens still found in Nbhd, the screens are called:
NScreen.bmp DiffN1-N2_8.bmp DiffN1-N3_8.bmp DiffN1-N4_8.bmp ness01.bmp ness02.bmp ness03.bmp
Where the non-US versions have "_Loc" added to their names.
As with the bars and buttons, replacement is a question of extracting and editing, bearing in mind that the tiles and other objects on a lot will always overlay the background. But when that's finished, there's the name to consider. I have both UK and US installations. To have an edited neighbourhood file show up in my UK Unleashed installation, I should call it "NScreen_unleashed_nonus.bmp" (no need to extract/edit the water files). If I want to use it in a US installation, it has to be renamed "NScreen_unleashed.bmp". It's still the same file, of course. To avoid confusion, I could just copy "NScreen_unleashed.bmp" to "NScreen_unleashed_nonus.bmp", replacing both defaults. For pre-UL installations, the same applies to "NScreen.bmp" and "NScreen_Loc.bmp". The visitable neighbourhood screens fortunately each come in only one version.
As far as the main neighbourhood is concerned, the choice between US and non-US is all you get - and it's a choice made by the game at loading time. It is not possible - at least, not without some third-party program - to have a different graphic for each neighbourhood. The same goes for the visitable areas; one Downtown is all you get.
Lastly, the splash screens. Again, it's a question of extract, edit, and have a think about the name. In a US setup, the replacement screen is simply called "setup.bmp". Set the installation language to Korean, and the replacement screen should by either renamed or copied to "setupKo.bmp". The splash screens really do look different for each language, so here it makes sense to create a replacement file for each default. The names of the splash screens are:
setup.bmp Setupde.bmp SetupDN.bmp SetupDu.bmp SetupFI.bmp Setupfr.BMP SetupIt.bmp Setupjp.bmp SetupKo.bmp SetupNO.bmp SetupPg.bmp SetupPo.bmp SetupSC.bmp Setupsp.bmp SetupSw.bmp SetupTC.bmp SetupTh.bmp setupuk.bmp
A bit silly to have a separate UK splash screen... Ah well. Happy editing.