Am I able to get a 450-500cc butt implants? (Photo)

Some surgeons would put an implant that size into your tiny buttock. This will most likely fail and result in months of follow up aspirations and ultimately removal.  I've performed over 400 buttock implants with very little complications. The reason for this is because I am careful with the patient and the sizing.  I would not do a 500cc implant on you. Please be sure to chose a board certified plastic surgeon who specializes in buttock implants and has extensive experience in performing this procedure. 

In order to pick the ideal buttock implant size you have to take into account your buttocks diameter and size; please see link below to help you choose the ideal maximum implant size.

One of the most important factors in creating the perfect derriere with implants is indeed selecting the right size AND shape. I have found the best way to assure this is to simply measure the actual dimensions of the patient’s buttock cheeks. With these anatomical measurements, I can select an implant that not only significantly augments the buttock but also supplies the correct 3-dimensional enhancement to look as real as possible...even in the most petite patients. Traditionally, teardrop oval implants have a 30+% risk of rotation and thus unnaturally change the buttock shape/appearance when doing so.  However, one year ago I created and patented a new "Stanton Anatomic" shaped implant that avoids this issue - not a single rotation problem in 200+ patients. The benefit of this is the fact that ~80% of women patients have more of an oval shaped buttock cheek than round, thus creating a much more natural and harmonious buttock contour. Thus, the only way for you to know what implant works best is to consult with a board certified plastic surgeon specializing in this procedure and have him/her take your measurements before selecting an implant and proceeding with surgery. 
The largest stock buttock implant currently available in the USA is a 750cc round implant. For the implant brand i prefer and my Stanton Anatomic Oval implants, the largest is 600cc. Indeed custom implants can be ordered larger, not only at a premium price but at a premium risk for most patients'. Unlike breast implants which are placed under the very expandable tissue of the breast and half of the pectoral major muscle, buttock implants should only be placed under or at least within the largest strongest muscle of the body, the gluteus maximus muscle, which is not nearly as expandable or forgiving. Thus most patients simply do not have a large enough native buttock muscle to fit an implant much over 500 ccs', without leading to significant complication such as wound breakdown/opening &/or implant exposure...necessitating removal. If a patient wants larger implants, 9-12 months after the initial implants have settled in to place and the muscle relaxed/stretched, then a second operation can be performed to replace them (similar to the process of going bigger with breast implants).   

Be aware, the "subfascial" space that is sometimes talked about is not a real potential space to place a buttock implant. It is essentially the same as a subcutaneous pocket (ie on top of the muscle/under the skin and fat layer only) and therefore should be avoided at all costs.

Some of those sought after video-vixen and celeb-types (without mentioning names) with cartoonish bottoms could have either gotten extremely lucky with a huge oversized implant (very unlikely if properly placed under the muscle), had a very large volume of filler injected such as silicone, PMMA, Sculptra, or hydrogel - all NOT recommended because of high risk of severe infections, migration and/or hardening over time,  and even deadly consequences in rare but significant instances (if mistakenly injected into the blood stream); and/or have been genetically "blessed" - although quite unlikely.