Wow! This is really, really cool!
I haven't entered combat yet, but the nav is excellent!
To stop the jumpy loading of wall sprites, give each sprite a negative sprite number except the last one that's loaded. Then they should all load at the same time. Like this:
SPRITE -1 sprite1X sprite1Y wall1.gif
SPRITE -2 sprite1X sprite1Y wall2.gif
SPRITE -3 sprite1X sprite1Y wall3.gif
SPRITE -4 sprite1X sprite1Y wall4.gif
SPRITE 5 sprite1X sprite1Y wall5.gif