To memorize the major system for numbers 00 to 99 (and 0 to 9) I've used emojis instead of pictures. I've changed the words to fit any available emoji. (if you find any errors or improvements please let me know: jakov(Q)
gmx.at)
The cards are in both directions. It's important to quickly convert the picture to a number, but it's even more important to quickly come up with a picture for a certain number (which could help in every day Life if you need to memorize a number). I think the system can be learned the best if you first learn from word+emoji to number and then reverse from number to word+emoji.