I got a company laptop because of my work. And if I wanted to ask, I can put stickers on it. So far everyone has seen my razer sticker and none of my work colleagues has complained (I'm still a trainee). Am I allowed to or not?
Do not do that.
I would not do it. If you have to give it back and the stickers don't come off, it won't be nice for you. And as a trainee, I would get a permit.
Better leave it.
It depends on whether the company allows it or not.
Since it is a device provided by the company, you should rather leave it (especially as an apprentice). Often these devices are leased and when it expires IT gets trouble and they pass it on.