I'll do what I can, 

Square beams get a better grip,

P.S. I am better after (obsesively) studying your gallery

Hope this isn't too much to say but...

The black text is hard to read.
The lightest color of green is a little hard to define and alot of the greens are way too similar.
I'd remove the palette or make it smaller.
The rings of the tractor beam are squareish?  Circular ones would be nice.
That diamond star sticks out quite a bit and the stars around it seem to "clump together" with it.
Make more tiny stars.
AA would be nice on the grass.
Remove one of the greys or make the difference between them more noticeable.
Make the black outline on the ship a dark grey or remove it alltogether.
The green outline on the guy bothers me...
Maybe add a shadow underneath the dude getting sucked up?

Hope I didn't overwhelm you.
This is some of your best work yet!

BTW, 17 colors right now.