Sony Europe has just confirmed that themes are now available from the Playstation Network Store for those who own Poker Night 2. When navigating to the PSN Store in Europe, do a search for 'Poker Night 2' and as long as you own the game, all 5 themes should be available for download on the Poker Night 2 product page.
We are aware that PlayStation 3 users in Europe are unable to download the themes awarded for winning in-game bounties. We are working with Sony to resolve this issue as quickly as possible. The issue is affecting themes only; Borderlands 2 unlocks are working as intended. We apologize for the inconvenience and will update this thread as progress is made.