StickerDrop by Gigi_Girl_Dev

StickerDrop is a lightweight webpage decoration toy for Firefox.

Choose a sticker and size from the toolbar popup, then place it anywhere on the current webpage. Placed stickers can be dragged, rotated with a double-click, or resized with Shift and the mouse wheel. You can also spray several stickers at once, trigger a temporary sticker-rain effect, undo the latest sticker, or clear the page.

StickerDrop only modifies the current page when you use it. Decorations are temporary and are not sent to an external service.