I don't think it's right. I always use generic thumbnails or try to at least have a picture as relevant as possible to a specific point in the video e.g Thumbnail:
Video title was "Defiance Gameplay - Part 47 - USELESS COOPER". Sometimes I do wonder if my titles and thumbs are misleading though but my titles are also for my personal reference to remember what video is what (it actually helps me find videos really quick if I need them), so I worry that sometimes it's misleading people. My generic thumbs look the same but with the part numbers changed normally, so those I don't worry about. As I'm not very creative in drawing from scratch I try to utilise as much creativity that my brain allows but I always try to adhere to the title and what is in the video, in this case 1 of the NPCs 'Cooper' was being useless and it was a small topic and something I felt should be highlighted in the video lol His methods are a prime example of why YouTube needs to stop promoting bigger YouTubers. If Joey actually died in this video, okay fine. If he's referencing or mentioning it as a small topic in the video than I think it's fine. But he might have wanted to be more to the point in the title like what the ENTIRE video was about or if it had multiple topics than put those multiple topics in the title. Unfortunately as a gaming channel I can only fit so much in the title at times :/