Animal Crossing New Leaf megathread: The economy of Bells, Fruit and Turnips.

Is there any way to get more than 10 patterns on you at once?

You can save up a fair amount in your pattern storage (Talk to Mable), but switching them out will always replace the pattern of that slot everywhere else except for shirts villagers are wearing and your town flag. The only way to prevent patterns from replacing each other is to create an extra character in your save game that's used as a pattern mule.