Themes on a Nokia phone - I hate them!

I've just got a Nokia 6303 and prior to that I had a 6500 - I can't
stand the "themes" - all I want is a display on which I can maybe
choose a colour I like.

I know I can change the wallpaper but I still get irritating remnants
of whatever theme it is sitting behind my calendar when I go into it.

Am I missing something fundamental here - is there a way round this?!