Okay, short review:
It is too small for more than 3on3 and too bland for long-time-motivation.
It is okay for a first map, but no piece of art people will like for more than 5 minutes. That's why no server admin takes it into cycle. It is an early piece on your path to a decent mapper. A piece you probably learned some basic things you can use in your next, better map.
Most points have been mentioned, keep on mapping and learning. Read some tutorials, load other maps and have a look at layout and decoration, at lighting and balance. Size is not equal to quality, keep your maps reasonably sized, not too big, not too small.
Make a few more maps and maybe your 3rd or 5th will be nice, well accepted and played much.
You cannot know everything while mapping your first piece, but you can learn with every brush how to get better, so keep on mapping!

Danny