Postby Fuyu » Sat Feb 11, 2017 2:01 pm
Your question can be interpreted two different ways, and I'll try to answer both as fully as possible.
Case 1: You want to add a custom tileset without replacing an already existing tileset. If that was your question, this is possible in SMBX 2.0. There are extra blocks you can replace in order to suit your needs. These are limited, however, and you might find yourself having to replace other blocks if your tileset is too big.
Case 2: You want to add a custom tileset shared throughout the entirety of an episode/project that you're making and don't want to put it in every single level folder. If this is the case you can simply paste the tileset in your episode/project folder, which is the same as where all of your levels will be located. Since their location is the same all levels will have access to whatever graphics you put in there. Keep in mind that if you do this you shouldn't attempt to paste the same files inside level folders