If anybody wants to contribute some UI elements or themes, I can put them in the Control Panel. You will of course get credit within the app. Send me a PM with the ZIP/PNG and a screenshot (if you can).
SystemUI: if you have a themed SystemUI.apk, just zip it up along with other apks to match (like DownloadProvider.apk, ect). If it's a background, I just need the png. Make sure SystemUI.apk and other apks are in the root of the archive
Lockscreens: make a zip archive that has the apks folder structure (com.htc.resources.apk). Example: res/drawable-hdpi - put any pngs in that folder (lockscreen_arc.png, lockscreen_arc_incall.png, lockscreen_arcglass_bottom.9.png, lockscreen_arcglass_top.9.png, lockscreen_prompt_back.png). Make sure your .9 pngs are compiled!
Overscrolls: same basic format as lockscreens. Make a zip that has the folders res/drawable-hdpi and contains overscroll_glow.png and overscroll_edge.png.
Rosies: same as SystemUI, zip up the apk. Make sure Rosie.apk is in the root of the archive.
Batteries: TBD.