So you're not an artist, no problem. VoxelMaker allows you to create any scene you can dream up and render it with lighting effects, depth of field, and more. What can you build with hundreds of tiny cubes? Probably lots of things.
A voxel is any sort of regular 3D grid that represents a shape or data set. It's used for making nifty pictures as in VoxelMaker, but it's also at the heart of graphical rendering technologies in games. Then there's Minecraft, which is basically one giant voxel editor.
VoxelMaker has a model editor optimized for touch, and it can accept .vox file inputs. You can share your creations as images, or export as .vox, .ply, or .fbx models. $5 isn't cheap, but this isn't the sort of app that comes to the Play Store every day.