Many people have covered they webcam with a sticker. They do this to prevent some bad people to take a picture of you.
I personal like this, but it misses a point. When someone is capable to access the webcam of your computer, you do have another set of problems.
Sure there are some software flaws that could allow access to the cam. For example via Google Chromes and a WebRTC session. But that would trigger the indicator light of the cam. A green, yellow or blue light next to the cam-slot. Therefore you can notice that the cam is active. A cover over the cam might protected against this type of software flaws.
So can assume that unless someone can control the indicator light, that you have to notice any usage. Does this mean you only protects against the usage case where someone is in control of the webcam hardware and is able to turn of the indicator light?
However to not turn on the indicator light you would have direct hardware access to the computer. There lies the issue. When someone is able to access the hardware directly, he can do whatever he want with the rest of it. You can install a keylogger to record any input. He can see what’s on your screen and he can install whatever software he wants onto the computer.
Most of the time this happens over a RAT (Remote Access Trojan). When such software is on your computer, taking a picture of you via the webcam seems the least of the problems.