When you are starting a new project on a small budget, you often run into limitations on your hosting service. For example, Heroku restricts the size of your website if you use their free tier for website hosting. If your website requires a lot of image, you may want to host those images using a free service, at least until you have proven your concept and are ready to start paying for premium image hosting (and you may want to consider a CDN as well).
There are many website that offer free hosting of images. These services are typically ad-supported and place certain restrictions on the kinds of images you are allowed to use as well as the size of the images. They may re-compress your BMP images to JPG in order to reduce storage and bandwidth costs. They may also remove your images if they start consuming a lot of bandwidth. For these reasons, I recommend using these free image hosting services only during the prototyping phase of you project, when you budget and user base are both small.
Status: This site appears to be broken as of March 30, 2013
status: Operational as of March 30, 2013