Use a free CDN service such as Cloudflare provides, make your web faster, boost SEO, security and save bandwidth.
What is a CDN?
A CDN (content delivery network) is a system of multiple servers which deliver website content to a user from the nearest geographic locations. Imagine, your own CDN consists of two servers in the London and New York. If your visitor is from America, then will be loading content from the server located nearer (in the New York). In the reality, eg Akamai (largest CDN provider) has situated over 2k locations around the world. Particularly, global content delivery networks (CDNs) such as Cloudflare, Akamai, or MaxCDN are storing (cache) a data on their own servers, thus they save your bandwidth and do all the work what should be doing your own web hosting. It's a kind of cloud computing.
Using a CDN, you can speed up and protect a website, secure website, and free cdns can save some money (because of saved bandwidth).
Free cdn for images
Definitely, most popular and best CDN for images and other static files is Cloudflare CDN. That's not merely content distribution that you can get totally from the Cloudflare. You can get free and really very fast dynamic DNS service. This service is good enough that is comparable to DynDNS (in general, this is the best one, however, in some English speaking countries is slower than mentioned Cloudflare).
Create own CDN infrastructure
Comparably to other kinds of files, images are the biggest files and their distribution can be made free and faster via Cloudflare, but Cloudflare doesn't offer free distribution of dynamic files (Cloudflare doesn't cache the html from your php files for free). Today, it can be very simple to design own private cloud architecture and create a CDN infrastructure that can be cheaper and performing even faster than some of CDN providers. You can just order some cheap VPS, dedicated servers in desirable locations. A wider perspective and more options can be to start from base and setup all of the environment via terminal, but now, i'm gonna bother you with a Linux tutorial, because you can deploy VPS/dedicated server and make it by one click applications. Digital Ocean, Google Engine and many of other web hosts offer needed software, but there's no so much companies making it so simple and cheap as Digital Ocean. More accurately, with Digital Ocean you don't need to take so much care about dynamic DNS and some other details included in the package.