I'm looking for three sweet french love poems, in the original french
(with an english translation) to put in a wedding gift (a framed copy
of one will be part of the gift). The poems should be short, not more
than 200 words, not less than 25, and classic, preferably 18th
century. Famous poems would be fine. I'm really looking for a french
equivalent to "She walks in beauty" by Lord Byron, but that's probably
too much to hope for. The perfect answer would be a trio of poems
which celebrate love in the time of Louis XIV.

This is from an earlier time, but it's a lovely little poem:

http://www.bartleby.com/244/26.html

This page links to poems in english and their translations to french:
http://216.239.39.104/search?q=cache:-Yo6ndhJEAEJ:www.keith-barnes.com/+%22poemes+d%27amour%22+%22love+poems%22&hl=en

Though somewhat earlier than you specify, and perhaps more
bitter-sweet than merely sweet, Pierre de Ronsard (1524 - 1585) is a
magnificent love poet. Have a look at the following web-site,
containing both the originals and English translations:    
http://www.lepg.org/ronsard.htm