i have two kinda formal knee ish length dresses, both maternity one's black with a pink and red rose pattern and the other is black with a blue pattern . . . dont have pic's at the mo but could take some if you like. and you'd be welcome to keep them if you want them. they we're given to me brand new and i've only worn them a few times!
i also have a teal blue dress same style as the others i brought to wear to a wedding so only worn once! has short sleeves but they have no hem as they we're altered at the last minute so you'd need to wear something over the top, which i did to hide my upper arms anyway!
hope that helps and if not that you find something x