I've noticed that every time I add a wallpaper or something to my Droid, I have to reboot it for them to show. Is this fixed in 2.0.1? I haven't tested it yet.
By "add a walpaper or something" I assume you mean "transfer a file to the Droid from your PC?"
Usually, if I open the Gallery after transferring a pic (or open the Music app after transferring an MP3 file), it does a "searching" thing for a few seconds, then the new pic (or MP3) appears in the list of available items... Is your phone not doing that?
Secondly, be sure you're deactivating USB-storage mode before you're unplugging the USB cable. Pull down the Notification Bar, and tap on the USB storage, then tap OK to turn off USB-storage-mode. That will force the Droid to "prepare" your SD card (which really means it's searching it for new files.)
I've never had to reboot to force my Droid to recognize new pics or MP3 files that I've dragged-and-dropped from my PC to the phone. But I've always "ejected" the USB storage device on the PC first, then de-activated USB-storage-mode on the Droid before trying to look at the new file(s).
Hope that helps...
Mableton, Georgia, USA