Band stickers are an inexpensive way of marketing and promoting your band however they work in a way which is different to how most people think.
I’m pretty sure that no-one has ever seen a sticker in a venue toilet for a band they’ve never heard of before and said “You know what…I like that sticker so much I’ll check that band out”. It won’t happen. I believe that stickers are ‘tags’ left by one fan to be found by another fan. It’s a system of recognition between your fans that only serves to build engagement and between the fans and that band and builds increased community between the fans themselves.
So stickers won’t get you any new fans but they will engage and strengthen the fans that you already have. I’d suggest you get a load and give them away for free on your merch table.