I made two sets of letters - one with handmade fabric roses and another with small red Styrofoam berries (found in the floral section at Hobby Lobby).
So, the puzzle was what to make the letter forms from, without spending a ton of money. Yes, it's easy to buy big letters at Michaels or Hobby Lobby... but four of them would have cost close to $50. I bought a 4x8 sheet of 1" rigid foam insulation and cut out the letters. The sheet was $13 and I think I've got enough for a lifetime of letters - it's hovering in the garage right now - and I must have 75% of the sheet remaining, even after using the same sheet to cut the circles for the cupcake stand. Cutting the letters was a mess - do it outside. I found a font I liked online and hand drew letters about 15" tall onto the foam. I used a utility knife to cut them out - but be careful. Then I used hot glue to add the fabric roses. For the berries, I spray painted the letters red first, then used modge podge and elmer's glue to add the berries (I'm still not sure which worked better) - that was a messy project too!
The photographer has the best photos of these - here they are: