(Inkscape SVG) contains the pattern I used (and the stars, on a separate layer). Hide the star layer, select all of the pieces of the crystal pattern, and group them together as one object (Object->Group, or Ctrl+G). Copy that object, and then paste it into your own vector on a new layer above your pony. You'll probably want to paste several copies onto that layer and arrange them so that they cover your vector in the way that you want, then select all of the copies of the crystal pattern and group them again (Ctrl+G).

Note that at this point the crystal pattern will extend off the edge of your vector. To fix this, hide the crystal layer and select all of the pieces of your pony vector (be careful you don't grab anything else, like pieces of the crystal pattern or background elements). Copy them, paste them

into a new layer, and then group them together. Move this layer above the crystal pattern layer, and then select your merged pony vector and the merged crystal pattern vector, then go to Object->Clip->Set. The merged copy of your pony vector should disappear, and the crystal vector should now cover only the area that your pony vector does.

