how come some people have avatars that are bigger than others; is there any way i can get a bigger forum avatar?

It's called toriprime or toriprime VIP.
Toriprime/VIP is a subscription that you have to pay for with real money to get advanced privileges on the forums (bigger avatars, more space in signatures, custom user title, username prefix, discount on broadcasts, etc.).
To buy toriprime, visit the torishop and click on "Mobile Boosters", or click here.

thanks i think i might get it!