Looking at the GBA tilesets, I noticed that most of them were just downgraded versions of the FE5 tilesets. I decided to take a look at the FE5 tiles to see if I could port them, and I noticed that the FE5 tilesets used 5 sets of 16 color palettes, just like GBA. I made the decision soon afterwards to remake all vanilla GBA tilesets as darker, more improved FE5-style versions.
Don’t count on any of them being fully compatible with the vanilla tilesets.
I’m working on porting FE5 map sprites to GBA, so that won’t be a problem for long.
Even without the FE5 map sprites, there’s the brighter version fit for the brighter GBA map sprites.
Looks like palettes 0 and 4 are messed up. All you need to really do for FEBuilder is import the tile graphics to the right and import the tile arrangement to the bottom left.
For tile animations, just go to the tile animation window and import water.txt into the ROM.