I would keep the current signature, and add a new one that looks something like this:
```objective-c
+ (UIImage *)mc_generateCircleImageOfSize:(CGSize)size color:(UIColor *)color backgroundColor:(UIColor *)backgroundColor

UIGraphicsBeginImageContextWithOptions(size, backgroundColor == nil, [UIScreen mainScreen].scale);
. 
.
.
.
if (backgroundColor) {
    self fillRect:CGRectMake(0.0f, 0.0f, size.width, size.height) inContext:currentContext withColor:backgroundcolor
}
```