In Wikipedia, a stub-page is listing for a page that has been noted but is still too short to be considered an actual page. All the artists listed have little to no information listed yet so it's a great starting point for brand new articles.
Black Lunch Table's task list is made up of visual artists of the African Diaspora who are under-represented on Wikipedia.
This is a list under development of missing articles on women who are (or have been) notable for their work as visual artists who work as painters, sculptors, printmakers, ceramics, fiber artists, installation artists, and other fine arts.
Another stub-page list of women artists.
A stub-page list of Feminism pages if you'd like to do the other side of Art+Feminism
Use the Citation Hunter to find articles that need help with finding additional sources. You can do searches for categories of articles that need more citations like "women artists."
One easy way to improve Wikipedia articles is to add Infoboxes to existing articles. You can peruse this list of Women Artists who need Infoboxes. Here is a tutorial on how to make an Infobox.