Thanks so much, I'm super flattered you liked the set!! :)

With better time (maybe in the summer) I could write a tutorial for one of these, but just to give some quick answers...
- the coloring on 3 is how I do most of my colorings: just individually coloring every part (all the pieces of his clothing, including the metal mask) to make sure there is enough clear color distinction between all parts of the icon. The coloring methods vary cause the same thing won't work for everything, but I mainly use things like Variations, Gradient maps (my favorite), Color balance, Selective coloring, basic color layers on various different blend modes (often Soft light or Color, but Multiply is surprisingly useful as well), and just everything, I always want to keep things varied just to make sure I don't get stuck with any routine. The important point is that all coloring layers are masked to only affect one part. This is super super slow and painstaking and will look like a mess unless the masking is precise, but I don't currently know any better way to get the effect I want.
- the coloring on 27 was mainly done with various gradient maps on soft light first to get to a type of contrast that I wanted, and once that was achieved I just put another masked gradient map over his hair (on normal but a low opactity) to get a little bit of color difference there. This was an easier icon to color since only one part needed masking.
- as for textures, I used different textures in all of these cause I wanted slightly different types and levels of grittiness in each one. A few of the ones I found especially useful are this and this by NYVelvet for the gridlike effects, and then there are tons of general grunge textures like this and this by innocent_lexys, but it really varies a lot (usually I try at least a dozen different textures on every icon until finally I just have to accept one... or five :P).

I know this is vague but I hope this helped a bit!