Sounds like an interesting idea. Do you plan on preserving the entire plant, or just the flowers? I had a neighbor that raised a lot of roses, and grew-out many new hybrids as "a tester" for Jackson & Perkins (before J&P would put them on the market).
He had a display (glass case that hung on a wall) showcasing many of his rose flowers. I have no idea how he preserved those flowers. It was a very attractive display and definitely caught your attention.
Maybe you could talk with someone at a museum in your area and ask if they know how to preserve plants/flowers (long term) for a display.
The 'preserving thing' sparked my interest, so I took the easy route (google is sometimes your friend) and found a link that talks about preserving rose flowers. It might be worth a read, and maybe it could also apply to orchids.
8 Ways to Preserve Roses and Other Types of Flowers - Dengarden - Home and Garden