The combinations I use are probably not as good for you as ones you would come up with for yourself. I would suggest just drawing out the numbers 0-9 and looking at the shapes and sketch a few things under each one, that look like that. If need be, rotate or flip the shape, or embellish slightly so long as they are all distinct. They should be easy to imagine objects that can be used flexibly. Salience for memory can come through things that give emotional response, so don't be shy about it.

and then use these to make simple stories like .. 13250 .. pen poked into the butt of a swan who yells grumpily and throws an egg..