Well, I was just browsing around the Acanthite website, and it appears the game is still being worked on. Now, I did not see any screenshots or anything, but if you want to use them, you're going to ask Fangking.
I would suggest you use the palette for Berry Forest (greenery palette with yellow as a replacement for the tree green). And remember, keep a backup before changing the palettes in case this does not work.
About your question on the tower, I doubt it will fit in the tileset. The tileset sizes you have to work with are fairly small, and that building is really big. I would recommend at least trying it, though, because I maybe wrong.