In the chat, people often feel the need to say 'vid' or 'video' to highlight that their post is a video.
The thumbnail of the video could instead be distinguished from a regular image thumbnail, by having a watermarked icon of a > play button or similar.
This is already the case in search results:
There has been discussion about a much needed overhaul of the chat room. This particular issue hasn't been brought up, but I think it's a decent idea. Chainer seems to be working on "big picture" updates/changes to the site, so he may or may not decide to look into this anytime soon.