Congratulations! It's a very nice piece.
I would double mat everything you create on paper in white (both mats) and use a neutral colored wooden frame (gold, natural wood, etc) in a traditional, simple style. Be sure the mats are acid free or the edges will turn yellow in just a few years and will cause your artwork to deteriorate, too. A gold filet is nice but adds a lot to the cost. That would be optional, depending on where a piece was going to hang.
If the organization running the show has specific requirements you should probably contact them to be safe. They might have dimensions in mind for the mats or who knows what. Try to phone them, perhaps.
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