Will lip fillers look weird with my small lips? (Photo)

You would get a nice result with fillers. Lip augmentations with fillers is a great option to improve the fullness, suppleness and symmetry of the lips. Results can be very natural-looking and will feel very natural. I prefer to use a micro cannula to inject the lips to prevent bruising. Look for a cosmetic dermatologist or plastic surgeon who is an expert in fillers to discuss your desired results and concerns and go over the cost of your procedure. 
I hope this helps.

Your result after lip filler treatment depends much more on the operator than any other element, and there's a large variation in talent among injectors.  For example, your downturned corners create the illusion of a frown (even though you're not sad), and that would be my first priority to correct with filler.  An artistic operator would likely improve definition and embellish your lips to a heart shape, turning your perceived disadvantage of a "tiny" mouth into an aesthetic advantage.  Long horizontal lips can never look like a valentine.