I really like all of these, and could probably make a case for each of them. :) I am leaning towards script for Sea Pony and san serif or script for Studio. For colors I like both combinations you've done. Colors are flexible for me right now; I know they are easy to change. But here are my initial thoughts, and I will look again with fresh eyes in the morning.
#13 Really like this type. Would like to see it with the "S" included in the type instead of the seahorse. I like the idea of that, but I'm not sure it's a quick enough read. I also really like the seahorse with the swirls on #16, maybe see how that one works with this type.
#15 Can we try one of the other script typefaces with the seahorse in the middle like this
#21 Same comment here about the swirly seahorse. Maybe it will be too many swirls in the end, but I'd like to see. That one feels very unique, but still very obviously a seahorse.
#24 I would like to explore these simple seahorse shapes (either tail direction). Wondering what it would look like with more of a brush stroke feel to the lines? Something similar to the typeface they are paired with.
I really like these, so thank you so much!