Well, here's Glee, for starters. XD
Dress Details:The dress I have in mind is inspired by medieval-style wedding dresses, because I simply cannot picture Glee in a big puffy confection of tulle and lace.
These are my attempts at recreating my pencil sketches:


(Yes, ouch.)
So, we have a light and simple dress, probably of a cotton fabric or something similar. The skirt hangs loose to ankle length, while the bodice is close. We have a sash around the waist that hangs down the back. The back is low to allow for wings, and the neck on the front is wide and scooping. We have loose bell sleeves, a little on the long side. There is no train, and no veil. If her feet show at all, they should be bare, or sandals at the very most. This is Ghlyssa, after all.
Colour:This is important. Ghlyssa and Riven are not going to have a traditional wedding. I would like Glee's wedding dress to be
pale yellow. The sash can be any of the following: darker yellow, blue, green, or teal. If you have another colour in mind, ask.
Other information:Ghlyssa's hair should be down. As I said before, no veil. I considered this, but I am in love with her hair and I think putting anything on top of it to hide it should be a crime. XD
She needs to be wearing this pendant:

She also should have a feather-and-bead accessory in her hair, similar to the one Riven wears. We're working on getting an image for this.
She can have her current "engagement feather." This one is similar in design to the one Riven wears made of one of Glee's feather. The feather is purple. The bead colour is, uh, undeteriminated.
There's also a plan to have a ribbon with crystal beadwork and the feather, again, exchanged as part of the ceremony. (No rings for them. XD) It's not really out of the concept stage yet, but we're working on that?