Very well done! These are better than most dawn of man leader screens I see for mods and also stay true to the original games design.
If you desire a critique I can offer one, but please dont take any offense from it, because, as said, I think you did a really nice job, especially for one whos still learning the design application.
1) The edges of the samurai can use a little more refinement; especially the first one. (But, as you said, you were learning it while doing it.)
2) The backgrounds are a bit too hazy. Im guessing their transparency was just increased in front of a white background. I think they should be a bit more vibrant, either by increasing vibrancy and/or decreasing transparency. Also, they should be converted to something a little more abstract/artistic and less like realistic photographs so that they mesh better with everything else. Simply apply a filter to it using some diffusion effects and/or surface blurring. If you want to get fancier, you can also try some subtle brush stroke effects too.
3) The fading of the samurai seems a tad bit excessive and perhaps should be a little more subtle, while also slightly more displaced and not just applying to the areas below the torso. Also, an eraser with a very feathered edge can be used along the bottom of the samurai (and perhaps slightly up one of the sides) for a more artistic effect, so that the samurai dont seem to run off the edge of the image. Perhaps, it would make them seem more a part of the image rather than just being in front of the image.
4) First, pardon my ignorance of Japanese/Samurai culture.

Im guessing theyre falcons, but Ill just refer to the images as simply birds. Anyway, I think theyre a bit too overpowering and perhaps they could be lightened or made more transparent. Another approach would be to use a line drawing instead of a solid mass (like the default game uses). You can try Googling for bird or any type of bird and make sure the filter is set to line drawings. You can also add the word tattoo to the search for more abstract and artistic line drawing results. Also, you probably dont want anything too abstract and minimal, because you want them to be ornate to get that tattooed effect.
5) Background positioning. I feel the composition of the last one (purple samurai) is beautiful with the entrance centered between the main object and the map (perhaps nudge it slightly to the left; if the background isnt long enough to fill the right edge, just give it a stretch
or, then again, maybe just leave it as is so it isnt too obvious). For the red samurai, perhaps the background can be shifted/stretched to the left so that the branches form a background behind him and the map will be more in the open with less collision. For the yellow samurai, perhaps a simple mirroring of the background can get the nice rift between the trees centered between the two objects so that one can better admire the hills and water down below. The first one, even though the background isnt as interesting, has a nice composition and the mountain is in a good location. Also, the grass line seems nicely aligned vertically along the samurais waist and top of the horses head (which also helps view the horse since its transparent).
6) I liked that you removed Asia from the map layer. Since, for most of use, Japan's location doesn't really need any additional visual context. Since you no longer have to worry about the rest of the map, perhaps you can scale down the size of Japan slightly to help with the overall image composition. But not too much, since its such a snaky land mass. Especially since your samurai seem slightly larger. Or, I dont know, perhaps this isnt needed once you see what it looks like.
