I have been away from the game for a while and when I came back I purchased the 2 newest Theme Decks from PTCGO Shop. To my surprise the boxes for Twilight Rogue and Tropical Takedown look great. They actually look like boxes with full arts instead of outer packaging we see in the Shop.
So my suggestion is to let players choose these great looking boxes for our custom decks. The Twilight Rogue box would look great for custom Lycanroc-GX decks.