Appearance Settings changer.

wallpaper changer is integrated into XrXca's PAM MOD r21b, you could look through the source and figure out how its done, or just message him and ask him about it. Don't know about the other ones.

Yo, Tut-dude:

One proggy which does a few of these things is called "Desktop Architect" (DTA). No longer in development, and I can't recall where I got it, but you can google & find it. Is freeware (but prolly not open-source), and I've used it portably in the past.

1) Don't think you can use it to change resolutions; at least I see no setting to do this.
However, there's a host of small proggies (applets) out there that are free/liteweight/portable to do this.
Two I recall by name are "QuickRes" (a ZDNet freebie program, AFAIK) and "MultiRes" - google 'em...

2) DTA can change your *wallpapers*, as well as screensavers, startup/shutdown screens, icons, cursors/pointers, etc.

3) In so doing the above items, you can largely "theme" your own desktop. But if you're a guest on someone else's PC, you're outta luck - cuz then you're limited to whatever stuff they have lying around on their system to choose from.

4) Height of the Task bar: I don't think DTA covers this.

5) Remove the settings on exit: Never tried this with DTA, but you can experiment for yourself once you've got it running:
Make your desired changes, click "apply", and then simply refuse to "save" your changes whenever you exit the program.
It's a reasonable guess that upon reboot, the desktop may well revert to what it was before you started messing w/ DTA. Try it and see whatcha get for results, then post here to let us know, eh?...

Happy hunting & experimenting!