well, if your game screen scrolls, then here is what you can do...
instead of redrawing every map tile every loop, only redraw the ones that are within the screen boundries. there are several ways you can do this, as I have done it many times - and it does improve your game speed.
tilex = int(xoffset/tilesize)+1
tiley = int(yoffset/tilesize)+1
the above equation should give you the grid number x and y for which to start drawing tiles (depending on how you determine your offset variables, you may or may not have to add some absolute value stuff in there), and lets say your screen can only fit 16 tiles across, and 12 down... so then you'd put it in a loop like this...
for y = tiley to tiley+12
for x = tilex to tilex+16
...blah blah...
next x
next y
...but then again - if your screen is constantly containing 25 by 25 tiles without going out of screen borders, then I wrote this whole thing for no good reason.
PS
Hi zen - long time no see. haven't done any pixeling lately have you?
Shoot for the moon. Even if you miss, you'll land amongst the stars.
