I think any 'wet' glue used over a large area has a tendency to warp the paper as the liquid in it is absorbed. Is there any way you could use a tape,(I don't know what the design looks like, lol), or maybe stamp the image onto acetate, then glitter the back of the image, then add it to the card?In which case use something like a clear drying PVA glue. Because the acetate can't absorb the liquid from the glue, it won't buckle. Then you can add it to the card with a blob or two of silicone glue. Here
on my blog is a couple using this technique. Or could you stamp onto a sheet of sticky backed clear film, then apply the glitter to that? Here
is where I did one like this using sticky backed film & gilding flakes. Hth.