It's a made up species, but I did look at lots of photos of seahorses. I'm not really sure which species I was looking at though, since I swear I couldn't find two sea horses that looked alike!
The model has 3465 surfaces before subdivision, all quads and triangles (mostly quads). About 75% of that is from the bevelling to get the ridges on the body and tail... each bevelled body scale is 5 surfaces that were created from one surface, so as you can guess it was a lot fewer surfaces before I did that. All told, it's about 14K after subdivision... large, but not too unweildy.
The rock is about 860 faces before subdivision. It's made from a cube I divided a number of times, then ran the noise plug-in on... much fun if you haven't tried it! The background and grass are just quads.
Here it is before and after subdivision. I tweaked the scale after subdivision. I usually commit my subdivisions before texturing, otherwise my UVs tend to warp funny sometimes.