Originally Posted by
mrgreenthump
As Artorius said, there are plenty of design cases and monitors out there. But if you want to hide the case, you need to make sure you have ventilation for the components still. As to hiding everything else, it depends on the table it sits on. It's impossible to hide cables on a glass table, but it's quite easy on everything else as long as you are willing to screw some brackets in for them to nicely go along the edges and won't hang to the side etc. Then it's just up to get a decently looking mouse+keyboard and you are done, additionally you can buy headphones to hide them when not gaming rather than have speakers on the desk.
As to just gaming on a TV, it is possible, but rarely something recommended due to the poor gaming performance of your average TV.