In CSS one way is to set a background position to center/center like background-position: center center;For later browser support maybe background-size ("cover" to crop while "contain" to keep aspect ratio within container dimensions), and "object" properties, but I don't recommend using those just yet since they're not widely a standard.
Not sure if it's a bug, but if it's not then it's really weird. If search is enabled you'll only find videos when using the search function and it won't find anything else on the forum (like topics). I thought it would include videos in the default search result if there were a video that matched the search criteria, instead of only displaying results for videos.