Tyroz

If you're inserting all new tiles then you won't need the old tiles and palettes and you can replace whatever you want.

Well I'm afraid you're limited to those 12 palettes. :/ You can recolor the tiles you're inserting so they're the same as the current palette, or if you're using palettes 7-12 there's often a lot of free space. If you're only making minor edits to the tiles and you want to keep the current ones there's not much choice you have.

If you insert new tiles, it only overwrites what you replace. In my case, most of the original tiles are gone because of the new tiles. Try looking around on deviantart for tiles. I got most of mine there.

Try again, I made some space. Palettes 7-12 are all palettes that are used for the secondary tileset (for example, the houses and lab in pallet town). So if you inserted a new tile using palette 7, and you inserted it in the pallet town secondary tileset, it would only work in pallet town (or other places using the same tileset). It's kind of confusing so let me know if you need a better explanation.

If you're still having troubles with tiles show me what you tried to insert and the exact steps you took. The only reason I can think of why there'd be a black block would be if you were incorrectly using palettes 7-12 and/or the secondary tilesets.

Oh! I'm sorry! I wasn't thinking. :\ Sorry about that!

Hehe nope i'm from Holland, thanks though :)
You have a happy thanksgiving too!

Hey, thanks for the request :)
I'm always glad to read messages like that, it's great to see that you like it ^^
As I said before, if you ever need help just ask and besides all of that:
Have Fun! :)