rough sketch edit that doesn't follow the grid at all! but I have, in the past, made tile sets with blood sweat and tears, so I know this kind of idea definitely can translate into tiles and tile variations etc!
So I looked back at when you were choosing whether to go with dark centers or filled in tiles and I absolutely am of the opinion that dark center is the way to go. The one instance where I think the filled in tiles works is on thin platforms about 3 pixels thick.
So this is an idea about where you could go when you make variant tiles or variant tile clusters. My experience with working with tiles is that you'd think you'd get the most mileage out of 6 one-tile variants, but actually using variant tiles I've noticed that variations that span larger distances (like 3 tiles tall, an entire 4 tile corner, etc) that have a distinctly different structure than the regular tile set will do much much more to give a more organic feeling to the entire piece.
So I'll go through some of the edits from left to right!
- I think one of the best things to realize about a tileset like this that has a middle piece, edge and corner pieces like this, is that every side can look very different as long as they're bridged together. There is no actual reason that the upper edge and the lower edge should have a similar structure - they'll always be bridged somehow regardless.
So I showed this by making the bottom edges have a stalactite kind of feeling to them. It's kind of an unimaginative solution but it's just to demonstrate that the tileset might become richer if there's a larger variation within it.
- The 3x3 block isn't super sexy. The way it's composed of tiles that bridge toward black without having a full block of black within it makes it feel a bit like a sphincter - here's a perfect variant tile opportunity! having a tile that makes it look like a full shape instead of a butth- .. donut!
- The entire right side is ideas about variant tiles that, in parts that are thin, break up the dark middle and make it feel more physical. I think the large dark void looks good on big tile pieces, but on thinner pieces of ground I think it's a good idea to light up more of the rock to make it feel more solid and physical.
... lots of words, sorry. I hope this will be helpful for you. I had fun with it, anyway, so no matter.
Good luck.
