Oh yes! Just what I have been waiting for. I have started modding those icons as well. You use very bright coloring, I am rather fond of more discreet icons in monochrome. But I might "borrow" some of your your shapes, they are very clean and very easy to discern.
I would also suggest making some atmosphere effects less intense, especally the swamp planets followed by the ocean ones and continental (and I would presume forest but I have no images to check right now). The atmosphere effect is just a bit too much. Maybe half the effect, its hard to tell without an image to judge. Event the volcanic planets are very red, Ice and barren are ok to me, I wouldn't change them.
The problem with planets is that the images are used in many different locations. On the main screen, the planets are looking good, but in the colony list and expansion planner, they look rather odd since there is no shadow there.
I borrowed your idea of surrounding ships with outlines, but I do not use colored outlines, just black ones. I found that when outlining ships and starbases, they look way better if they are positioned on top of other ships or planets.