Absolutely. Like I said, they are commonly used form elements on so many websites. I did get some buttons and combo boxes from Filament Group. They're doing some good work. But to include them in the TR theme would be a big help.
We are definitely planning on creating a full suite of ThemeRoller-ready custom form elements this year. We just want to work through all the elements in detail in a comprehensive way instead of doing this piecemeal. Stay tuned to the planning wiki: http://jqueryui.pbworks.com/