Just have in mind that another server to serve your images would add another TTFB, which is usually around 100ms to 300ms just to serve images. it's fine if you have a lot of images, but too much if it's only a few.
I am using MaxCDN in conjunction with Cloudflare Free Plan and was able to reduce my loading time from 1s to under 600ms that way.
I have 3 cnames on MaxCDN: cdn.domain.com, cd1.domain.com and cdn2.domain.com.
I use cdn.domain.com to serve images, cdn1 to serve CSS and cdn2 to serve JS.
Cloudflare is my DNS Provider and also serves HTML. this way, very little is actually served from my server.