I just started modding recently and was trying to figure out what the return value of getRenderType did. Since I was trying to make a gate, I was working with fences and doors, which used render types 11 and 7. After experimenting, I found out that it changes the shape of the model, for '0' it is just a cube, but for any shapes other than a cude there is a different number. So I searched through all the block java files to see which blocks used what render type and created a list of them. I thought it would be good for me to post the list here, since googling and searching the forums didn't help me at all.
Yes, that is what it usually does, but of some reason when using rendertype in my code, it will just be a grey ugly picture in the quickbar. I can see its name and the block that comes out is not the one thats pictured in the quickbar. And I've testet and found out that it is the getrendertype that makes it happen :/