Card Alter Education Project
I do alters myself, play with them casually and sometimes at events, and also run FNM at my LGS during which I've told people yay / nay regarding them using their alters at FNM and other COMP REL events.
My guidelines are fairly simple. These apply to everything but basic lands, usually I'm fine with basic lands as long as they are made from an actual basic land and the name is intact and it is clearly the land it's supposed to be ( IE not a mountain made to look like an island )
All alters must be sleeved and the paint should not effect the thickness of the card ( if you look at the top of the deck where the sleeves open you should not be able to see it ). Transparency / printed paper / other cards / etc. cannot be glued to the card.
Extended borders / full-arting a card needs to use the original art of the card so that the card is still recognizable. ( IE not replacing the art / borders of a Hazoret the Fervent to be Hades from Disney's Hercules ).
All text boxes must be intact ( except for basic lands, though the name box should be intact ) especially the name and type bar. This is the biggest deal breaker for me, and most alters I've nay'ed have been because of this.
Your altered full art Torrential Gearhulk may be awesome, but you covered up the type bar and therefore it cannot be used. That's a pretty sweet altered full art extended border Mountain, but since you covered up the name ( and the entire card ) it can't be used.
TL:DR
o Don't cover the name / type bar ( basic lands don't cover the name bar )
o The card needs to be recognizable at a glance