Of course Vince would like guys who would look impressive on TV, may it be ripped physiques or being giants or whatever, but don't use that as an excuse for a smaller guy not getting pushed. There's other reasons to factor in like CC's point about non-homegrowns and sometimes believe it or not, some guys don't get pushed because they rub the management the wrong way (Chris Jericho currently comes to mind).
edit: Not to say being small isn't a reason that people don't receive pushes, but if they have other intangible factors, Vince will push you regardless of your size.