Unfortunately the game only allows for each user to have a maximum of 12 presets at any given time. If you'd like to have more, you could always consider using a backup account for them
And yes! There is a way to change the numbers. Firstly, go to all the files and rename each of them, replacing the number with the one you want (so if the file was originally called "preset_7head.jpg", and you wanted it to be preset 1, the only change you'd make were so it was "preset_1head.jpg" instead). Once that's all done, you open up the preset's material file in a program such as notepad, and wherever you see the number "7" you change it to whichever number you'd like (then save)
I hope this makes sense