SDK Spriter has been an interesting title on Wii U eShop, though it hasn't yet fought through our backlog for a review. It's understandable why the concept is appealing - it's an app that promises a whole lot of tools for creating retro game art for maps, sprites, tiles and levels. There are then some options for creating small playable experiences with those assets, currently in three forms.
Overworld, Terrain, and Dungeon Master. Overworld levels present the player with an overhead environment similar to classic RPGs, including roaming NPCs. Terrain levels present the player with a pseudo-3D tilted environment similar to early racing games of the 16-bit era. Dungeon Master levels assist with conducting paper-and-dice RPGs, letting the DM/GM control on the Wii U™ GamePad™ what the other players see on the TV screen.
Upcoming DLC will add to this. A platformer level mode is on the way as a free extra, while a turn-based battle level mode will be a paid option.
Though it does look rather basic in appearance (like its predecessor), the ability to create, play and then share these assets is sure to be tempting. Let us know if you're an SDK Spriter user in the comments, or if you're tempted to take a punt on it - it's currently 20% off for SDK Paint owners.