Looking good for a start. I really like the trees. Can you really do 8x8 tiles? I thought the lowest possible was 16x16.
GBA only supports 8x8 tiles. Nothing else. All other tiles are made up of 8x8 chunks.
color contrast too low for GBA; use black for outlines and saturate your colors more.
Seems fine on SP/Afterburner (ie well lit) hardware, but you do have a point for older GBA without proper lighting. Since I am targetting emulators here (getting it to run on hardware is just a bonus) I'll probably keep the contrast as-is for right now.
house is pillow-shaded. At the very least, replace the shadow for a highlight on the top and overhanging edges of the roof.
Point taken, and will work on that later tonight when I get home from work.
not enough variation in the trees. Maybe a pine or two?
Add shadows under the trees, using grass colors
Doing that would cut down on the number of tiles I have available. Since I can't go over 250 8x8 tiles per map, this could cause a problem, and I don't really see adding a pine tree to this map (there is a winter region with pine trees in it instead of autumnal trees).
the trees are chopped off at the bottom-left of the screen.
That's because this was just a test map, to see what the tiles looked like on GBA hardware.
grass is too pale, make it greener or yellower.
No. I like the grass colour.