I grabbed my fabric markers and painted a simple leopard print on them.
If desired, you could paint your shoes with an according base. I left mine white.
Then just paint the spots randomly over the entire shoe, here green. Don´t pay too much attention on the shape, since the black outlines make it look like a leopard print.
Outline the spots partially; I figured, that outlining the entire spot doesn´t do the job. Let dry according the instructions of your marker, done!
Enjoy your new old shoes!