Firstly, the purpose of lights is for others to see them and act accordingly. Anything stuck on will reduce the light output, and carries a risk. In the event of a bump, your insurance company may quibble.
Secondly, as most lights are plastic, many glues can react with them. Before sticking anything onto them, ask the supplier to guarantee that the adhesive is compatible and non-damaging to the lights you have. Get that in writing. If they refuse, best not to take the risk.