Iv noticed a couple of people asking about inserting tiles instead of a pokemon centre etc, i see where the difficulties arise, the tilset for the pokemon centre, mart etc overlap, there isnt much room for additional tiles, and are based entirely on 4x4 tiles. To combat this (for example i wanted to insert an old style inn instead of a pokemon centre) You need the basic tileset (0) and the tiles you want to insert. keep in mind that because the tiles overlap you will end up with a new pokemon centre and mart of the same design. what you really want to do is divide your new tileset into 4x4 tiles, then look at it closley, you need to remove any of these tiles that are duplicates, this includes blanks, and both x and y invertions, once you have it to the lowest possible amount begin inserting over the pokecentre mart tiles, be cautious, you may have a few extra tiles here and there but there are also a few uneeded tile slots here and there. once done you will need to rebuild both the centre and the mart on your tilset, bit by bit replacing all y and x inversions.
If any one is unsure about any of these points you may contact me and i will help you out. i plan soon on making a tutorial for this, perhaps if it is okay with you Aljam I shall add it to his thread, then you wont get anymore such questions and will have a unique section of tutorial i havent found covered anywhere else.
That would be swell. It's always great to have everything in one place.