It is certainly feasible. You might like to have a look at a recent demo page by Eric Watson. It could easily be adapted to your purpose.
Of course, you could use CSS3 rounded corners... as long as you are willing to sacrifice IE users. (Yhat's what I tend to do, but you may not be allowed to. )
EDIT: actually, on second thought, if I had to use images, I would probably have a separate strip at the top and bottom of the site and perhaps use the doors as you suggest.