[RM2K3] I NEED MORE SPACE ON MY TILESET

You could also use an image editing program, take a screenshot of the map in event view, then add a new layer to the image and scatter around the graphics you want to use that are 'above' hero or inaccessible. Then erase the bottom layer of the map itself and use that image over your map. That is, parallax mapping.

I usually just use events since they're flexible, can be placed on any layer (below/same as/above hero) and easy to work with. You could also play with an actual parallax for anything that's supposed to be below hero (floor tiles and the like).

If it's more than one map, you could also use a chipset for each.

Try making the dimensions of the graphics within the tiles 16 pixels wide (that is, with 4 pixels on both sides empty). If you're placing them above each other, either use 16 pixels height and have them right above each other or 32 pixels high (the full charaset height) and leave a space between the events.

e:

1 - blank animation frame.
2 - this is used for if you want all graphics to tile and be set to a particular kind of layer (say, everything above hero or same as). The graphic (red) is 16x16 with 4 pixels either side and laying flat on the bottom. Events can be pasted around all sides and it will match up as long as they're all set up like this.
3 - this is for if you've something like a tree tile where only the base is set as same as hero and the rest should overlap. In this case the events are safe to paste side by side, but there should be a gap between top/bottom events to tile correctly.
4 and 5 - these can be used next to each other (4 next to 4 and 5 next to 5). They can also tile on top of each other.

Hope that helps.