Oops sorry for posting somewhat of a non-sequitur. I'm definitely not a designer (pixel art or otherwise), but Gamasutra often has solid community content and interesting deep dives across game design issues (like in the parent!).

See:

Basic pixel art tutorial: http://www.gamasutra.com/blogs/KennethNg/20151211/261577/Pix...

Deep dive into Crawl's pixel art https://www.gamasutra.com/view/news/300004/Game_Design_Deep_...

Another collection of pixel art tips (and examples) https://www.gamasutra.com/view/news/176663/5_tips_for_making...