DreamSpeed CDN can definitely help speed up larger amounts of images loading, by having it download from a closer geographical location. DreamObjects is currently only located in Irvine, California.
If DreamObjects is down, then the CDN will likely not work unless the requested geographic location has warmed cache. DreamObjects is where the CDN pulls its files from to warm up its cache, and that cache will stay warm for a while. If the cache has expired, it would need to fetch the objects again.
DreamObjects has gotten many upgrades in both Ceph version and hardware this year, and we are expecting it to have increased reliability and capacity due to it. It is less of a worry of the CDN not working due to DreamObjects now.