I'm considering framing [with or without a mat] this series and displaying them together; they are currently pinned on the corkboard above my studio table, and they do look nice as a grouping. With pastels, I sort of waver back and forth between whether to mat or not. I have matted and framed several of the small works I've done (~5x7") that are hanging here in our place, but in general, I store and sell them un-matted and un-framed. I've seen other artists frame them sans a mat, and they often look very good, but I do love the look of a light neutral-colored mat and a simple frame for pastels.
Number 5 is a switch to landscape format, as is #6.
pastel on w/c paper toned with black acrylic