7-8K images should not be a problem with using something like an external drive or a back up drive on your machine.
If you are looking for an online service you could pay for http://www.carbonite.com
A free suggestion for that many images depending on if they are RAW or not would be to use DropBox. www.dropbox.com
They offer a few gigs free and if you have an iPhone or iPad you can access any of the files from your phone as well. If you refer people you get more free space. I like the service quite a bit. It is a roaming USB stick for me that I can access all my important documents and images from at anytime.
If your image collection grows there are some alternative pro solutions out there that are more suitable.