I'd like to tell a bit about the software I'm currently developing. Kenney Studio is a tool which allows you to build sprites out of pre-made objects. Each object has it's own options (imagine a character head being able to change face properties, hair and skin tone) and many of these objects can be used to build multiple types of sprites.
Currently there's not a whole lot of content included yet because I started from scratch about a month ago, there are regular updates though and once purchased you get them all for free.
You can download a free demo for Windows/OSX on the page (doesn't allow exporting):
or keep an eye on development on our Trello board!