I'm sure this has been suggested already, but oh well.. here's another vote for it!
Many artists intend for their work to be displayed on specific mattes.. I think it'd be fantastic if dA implemented a feature to allow either the viewer AND/OR
the artist to choose between 2 or more mattes on which the deviation is set. It could be temporarily changed if the viewer is the one making the decision, or permanently changed if the artist is the one making the decision.
If you like the idea and think it could help make dA even better, please give it a shameless self-promotion: Staring At The Sun