Ok so I'm being stupid, but how is anyone going to know if you'll think your TV will look bad on your wallpapered wall. There's no hard and fast rule which says it obviously will look crap and anyone who thinks otherwise is a tasteless moron. It's going to be just down to your personal opinion of what looks good and bad in your room, which no one here has seen.
Personally, I find many wall-mounted TV installations look awful, wallpaper or not. Many people seem to mount them too high, such as over a fireplace, so you're then often looking up at the TV instead of level at it or down at it, and across the shortest length of the room to boot. Extended viewing from an average-height armchair or sofa would leave me needing a chiropractor. But even that's only my opinion, others are entitled to think otherwise.
When my youngest niece bought her first house with her gothy boyfriend, they painted the walls in their lounge purple and black. I thought it looked shite, but they thought it looked lovely. We're both right because there's no accounting for taste.