Failed on day 2/3/4/5, but found time to jump back on it and try to catch up. I'll call challenge #1 (Little Mermaid) done for now. Rough calculations, 10 hours of work in total went on this sculpt. Aiming to spend more on the ones to come.
I hope I'll come back revisit and finish some of the more interesting ideas. As a friend of mine Andrew Doma (http://www.andrewdoma.com/) recently mentioned in one of his posts "I set out with a mission to get better at character design (essentially, a large aspect of my job) by doing a few quick designs throughout each week after work."