And the creature is finished! I am now one third of the way through the final concepts, and I'm very happy with the final outcome.
The final sketches for the turnaround, which, now I look back at them, could have had more weight going down the front, but it's a minor complaint.
More last-minute colour experimentation - I found some photographs of marshes and picked swatches from them to work with, though I eventually went back to the colour scheme of #3 from the previous batch. Light on land in marshes is often dappled as it passes through trees, so I bore this in mind as well as thinking that the dapples could double as faux-algae when submerged in water. #7 was the final design I chose, and #8-#12 were just playing with HSL and contrast sliders until I found something I liked. In the end I went with a combination of #9 and #11 - I liked the brown of #9 but toned it down with greens and greys from #11.
And the final turnaround! I am incredibly pleased with the final result, though if I ever have to draw dapples again I may just cry. The design has a very swampy feel, and looking back I'm glad I chose to give it fur. I was initially hesitant as it had always been hairless in my head, but the hair helps to break up the outline and make it look more real. In hindsight I feel I should have worked more on the face markings, so I'll remember that for the next time I do something like this. The fact that I focused on its shape from the side probably didn't help this, so I'll definitely have to get out of my everything-is-in-profile rut.
Also, after I finished I noticed just how much from the front its face looks like a Turian from Mass Effect. Oops.