We're working on 2D tile sets for our maps, but we're not quite sure on the thought process for making a tile set. He understands what they are, how they're used, and he will be using the Tiled Map Editor though. He just doesn't know how to come up with how many different tiles will be needed, how to arrange them, etc. so we can create the maps in Tiled.

My suggestion was to first come up with a themes to group up all of our maps (cave, mountain, forest, town, indoors house, etc). Then, we would design a few maps in Tiled using a solid-colored block tiles to illustrate the layout of each map in Tiled. We could start visualizing from there, and come up with possible tiles needed to construct maps that'd actually be used in production.

What's the question?

I should have put this in question form, but it's here:

He just doesn't know how to come up with how many different tiles will be needed, how to arrange them, etc. so we can create the maps in Tiled.

I also gave a suggestion on how I'm planning on approaching this, but he's still wrapping his head around it. I'm asking if I could get advice on how to go about designing a tile sets from some one else who's traveled that road. The way I used to do it in middle school was how I described it above when I did all my own art.

Design prototype maps and tiles on paper. For example, if you have caves,

• sketch a few caves in the style you want,
• think where you could slice them into tiles and what transitions between basic tile types (e.g. cave walls, with different facing and possibly with different slopes) you need
• decide what parts of the drawing can consist of repeated tiles (e.g. flat cave floor, in dry and wet varieties, and vertical wall) or need unique multi-tile structures (e.g. in a multi-tile stalactite and stalagmite pair you can repeat only the empty gap),
• sketch the tiles and try assembling them together to test what constrained caves can be built from them,
• fit optional stuff to the tile grid (e.g.tunnel entrances: 1, 2, 3, 4, 6 tiles? Or even bigger?)
• invent variations of very common tiles (e.g. different bumps and rocks in flat cave floor tiles),
• and only when you know what tiles you need draw a tileset on the computer.