First I have to say I like this a lot. I like the simplicity of it, and the simple, bright colour scheme, and the feeling of freshness it has.
I think if I were to change this, I would want to make the shadows a little deeper around the A (and possibly a little lighter on the T) - the A looks a little flat to me in comparison to the other letters. I like most of the bugs, and I really like the little reptile peaking around the T, but the butterfly looks a little too flat for my tastes. Either I would try to change the perspective of the wings a bit in photoshop, or go foor a different butterfly, perhaps with wings slightly more together, perching on the top edge of the T if that makes sense.
My other nitpick would be the leaves, I would like to see a tiny bit more variation with them; while there are different sizes which is great I can see the same little flaws on each one.
Overall though I think you did a very good job with this piece of art
you need to create a better depth of feild, looks a bit off, and the perspective on the bugs is off too, and what is up with the middle of the R, its white, I thought we should see leaves through the hole.