You could try just putting up a web site with your proposed design, and ask people here to comment on it. (Or maybe in some design forum, if they’re not sick of such requests.)
Or just have it do something worthwhile, mention it, and people will go give you feedback. I recently launched SumOfABatch.com, as a home for the mead-making calculators, advice, and other stuff I had been putting on my regular coding-business page, mentioned it in a mead-making forum, and got some free design advice. 