It used to be OK at Coffield but they are stricter on the "homemade" now. You have to keep them simple and usually all in one or two pieces. I did a paper basketweave heart design a couple of years ago and it was denied even though it had no glue. They said it was because it was handmade, but the mailroom lady told hubby I had used too many little strips of paper.

I sometimes send photo cards, where I get a piece of coloured card, fold it in half, cut two diagonal slots across the corners on the "front" and then poke the corners of the photo through the slots to hold it in place. They are still OK.