In reply to Flinticus:
Endless possibilities.
It depends what you want, and what the wedding guests are used to and would like.
If you want upbeat, with content that some of the guests might recognise, and probably like, then this Naxos collection of Mozart Overtures is terrific:
http://www.naxos.com/catalogue/item.asp?item_code=8.550185
or, in a similar very hummable vein any of his early stuff will do, for example this CD of his Salzburg Symphonies, which is just great:
http://www.naxos.com/catalogue/item.asp?item_code=8.550108
Less well known, but deliciously joyous and jaunty, are these pieces by Jan Dismus Zelenka's trio sonatas, here played by Heinz Holliger and co
http://www.amazon.co.uk/Zelenka-Trio-Sonatas-Holliger/dp/B00000E41F/ref=sr_...
If you want something more modern, and quieter, without being sombre, how about piano music by Sati, Rodrigo, Ravel or Debussy:
Satie
http://www.amazon.co.uk/Satie-Gnossiennes-Gymnop%C3%A9dies-Piano-Works/dp/B...
Rodrigo
https://itunes.apple.com/us/album/joaquin-rodrigo-complete-music/id45613681...
Ravel/Debussy
https://itunes.apple.com/gb/album/ravel-works-for-2-pianos-piano/id26546297...
For jaunty keyboard music, half an hour of Scarlatti could go dwon very well, for example as played on a modern piano by Mikhail Pletnev:
http://www.amazon.co.uk/Scarlatti-Keyboard-Sonatas-Domenico/dp/B00005IA25
For ethereal, try earlier musics from the 16 C, for example by Shepherd, Byrd, Dowland and Josquin. Or try Monteverdi.
Schubert's German Dances and Moments Musicaux would surely not upset too many, and might delight a few.
Or try chamber music. Haydn would be a good bet for that.
Good Luck and happy choosing!