Hi! great work, but I have a few recommendations:
If you look at a real picture of a seahorse you'll notice their tails are a bit thicker than what you've depicted. (although, if what you've done is intentional, your style, etc. then I don't mean to impose.)
Also, I suggest thinning the chest area a little bit. But again, if this is intentional, then nevermind.
maybe the line going down the side of the seahorse should be a bit more knobbly.
Otherwise, very awesome artwork