I think I can manage this, with the help of this tutorial that I googled.
Something I haven't found the answer to though - I want to be able to change both the background div in #header AND in #headerimg - is this feasible?
Any help is much appreciated!
And the answer is....as far as I can tell, after some time spent searching and researching, it is not possible, or at least nobody's done it. :(
If anyone knows different, please say so. Hell, if you don't know different, drop in and say hi, or slap me up side the head - let me know I'm not talking to empty air?