I just came across this, downloading now. It looks pretty promising and it's "free" - http://www.mapzoneeditor.com/index.php (Not sure what its export options are, atm. But, bitmaps were mentioned.)

I got an earlier version of that included in a magazine cover CD once. I clicked around in it a bit trying to follow a tutorial and found it crazy-complicated, features seem to be hidden in odd places all over - sorta like Bryce. I didn't really apply myself to it long enough to really get it, but I'm sure it's very powerful once you know what you're doing. And free is always good while you're poking around looking for a tool that fits you.