Hi there!
There's a few problems I can see right off the bat, the first being that you can only have a 128x48 pixel background tileset (as well as a separate 128x16 screen tile set, a 128x48 path tileset, and a 128x32 HUD tileset). And you can only use one tileset at a time while the game is running, but the game can swap out tilesets when it switches screens.
Second, you seem to have your 16x16 tiles separated by a pixel grid, and it's making them all off center. If you want to use your tiles properly you'll need to erase the grid and bring your tiles closer together.
Third, you'll need to convert the image to BRGB (black, red, green, blue), otherwise the graphics will not show up at all when you compile the rom. It may look just fine in the tool, but I guarantee you it won't show up unless it's in a format that the tool can convert to CHR. Joe made a tutorial about it that you can watch
here.
Good luck!