-I think you should add more clouds to the right side to create more flow
-I think you should also up the contrast and try some brighter colors.
-And possibly more space stocks.
As said, I love the concept, and you're just getting back into photoshop. As said, not your best, but it's more of a sig to get used to the tools again. Keep making more.
Ermmm I really don't know what to say... There's just something that bugs me about it. I think possibly it's a bit too long horizontally? It would likely benefit from being shorter, and more compact - The stocks closer together, and overlapping more, mainly on the left hand side.