There have not been many themes made yet for the new Bold because RIM has not updated the software for making new themes yet. I won't be long and there will be some new themes released. Probably the same thing for the new ringtones too.
I think you can download any mp3 to use as a ringtone and any digital photo as a wallpaper, as long as it is the correct size for your Bold. The best format is .png for wallpaper.