A sheet of Mrs Grossmans stickers called Bubbles Small Frame from the Small Picture Frames range.
The sheet is approximately 100 x 80mm and has beautiful bubbles themed frames and four coloured border strips 3mm x 80mm. You could use the frame for one 2.4 x 3.5cm photo or for two photos, for a 2.4 x 3.5cm photo, and a 5.5 x 4.0 cm photo. The central piece could be used as a title box.
Acid free and lignin free and these stickers would be great for scrapbooking or making cards.