Here are my comments
For the first one:
Its good. I was thinking what would improve this is adding colour effects around the face trying to make the face the focal point. you could do this with brushing, c4d, blurring, and many different ways! Another suggestion I have is adding a border around the whole image, maybe like bars at the top and bottom or something. Play around with things, give it a shot! Don't be afraid to post it either.
For the second one:
There is something about the render... hmm. I think it is either too small for the image, or it does not match the colour scheme. Or both. Overall good job, I'd just use a bigger image next time, and tint the colours a bit differently.
For the last one:
Ah, you changed the colours which makes it match a lot better, but like I said in the previous comment, you should change the colour scheme, or use colours that have many more colours that you can match to it easily.
Great work overall! Just keep on chuggin, and try new things.