By buttons, I think you mean "icons"? I found some of my stuff on google using "blackberry theme Icons" and different variations of that. Royalty Free Icons & Clipart Stock Images ~ Icons Etc. is a great source. You will find how tedious and time consuming theme building is nonetheless lots of fun. Once you download your sets, and then see what icons you can use, rename them, resize them, and stuff. There are also great threads for icons here. You can also join other forums and find stuff there. Or you can come across people who would send you stuff for free. As far as ideas, those are up to you, and if you are the kind of person who takes requests from people.
