yes, its possible. i mix and match pieces of different themes all of the time.
Cydia>Search for "OpenSSH"
Then you SSH into your phone, Var>Private>Stash>Themes I think it is? I know the stash/Themes part is right. And then after that you copy the ICONS folder into your new themes name, and delete the old icons folder, and also the dock.png
uh not so sure how to do the accesses part
i dont really know how to SSH