Well thank you very much for the welcome.

You can, indeed, import your own tilesets in RPG Maker, but you can't edit them inside the program. The program (I believe) is also limited on its grid sizes. I think the older ones only handle 16x16 tilesets and the newer ones only handle 32x32 tilesets. I could be wrong, though. I think RPG Maker handles bmp, and maybe png files. And like I said, you can't really use the maps you make in it for anything other than RPG Maker, since you can't export the maps you make.

However, I'm looking into a program called "Tiled" and so far it seems to be pretty good foy my needs. I can't find any videos of it, but it looks to be pretty similar to the RPG Maker map editor, but you can make infinite layers and you can export each layer to image formats. Here's a link:
http://mapeditor.org/