I don't know what your goals for this product are, but at €0.99/month, you're going to need thousands of paying customers to make any noticeable amount of reven

I don't know what your goals for this product are, but at €0.99/month, you're going to need thousands of paying customers to make any noticeable amount of revenue (not even profit). You might want to try selling sponsorships directly to relevant companies or raise the prices significantly and serve a smaller market. There is no dearth of free photo sharing apps, so maybe it's better to sell some premium services which the free apps don't.