Stella is a little too tan.
Check it, it's season one wings!
I found these while going through the internet (I think Angela's Winx World) and also reading the Oblivious Prattler's post about this and I wonder, are these real? Also, I could not find Tecna, Musa or suprisingly Layla's.
Actually, I found one for Layla but it's the chibified version from the video tutorials on the official site. Once again, season one wings!
This seems to prove that they will have one adventure under the sea at some point in the series (Maybe season five?) but this could be false. Although, why they bother making mermaid stock art of such good quality if they never use it? Is it possible that while Layla is getting ready to get married on Tides that the girls will have some type of underwater adventure?