Hey, i like your 3d concepts, you should try to put them into a scene instead of just t-pose renders. give them some environment, compose an interesting shot (the warrior e.g. could look cool shot from below standing on a cliff on a far away planet or in soe sort of wasteland?
try to light it interesting
my advice regarding your paintings would be to practice drawing more to get a feelign for propoertions and maybe you can try to use colors more deliberatly. try to balance thigns out and to create a focal point. for exaple in the picture from post nr2 everything is very saturated. you could try to tone down the background, make it less saturated and a bit darker to make the figure pop out. you could try to put a bit more time into rendering out the face so you have a variety in shading details, looks more itneresting than when the whole image is rendered the same way!
keep it coming