You might be able to utilize something like AWS S3 storage which is low cost for the storage but AWS will also charge you for I/O to/from S3. This can become very costly if you transfer alot of data into/out-of AWS S3.
Remember with a Cloud provider you have to pay to transfer the data IN and to transfer the data OUT.
Have you priced what a faster internet connection would cost you?
Or a 2nd Internet connection just for this video traffic?
Look beyond the Cable MSO's also, what is a FIOS based service's top speed?
You mention you BMP images being ~5MBytes (I assume mb = Meg Bytes and not Meg bits). Your current Internet is 100Mbps so one of your images takes 40% of your entire internet connection when being transfered (5MB x 8 bits = 40Mbits).
It takes an image every 3 to 5 seconds.
It seems to me that your problem may be more the bursti-ness of this traffic that cause you problems not necessarily the amount of data. Your internel "work" network is being hit every 3-5 seconds. Assuming your internal lans are 1Gbps ethernet this still shouldn't be a problem unless its your co-workers complaining that their "internet" access is too slow when 40% of the BW goes away every 3-5 seconds while transferring the image.
Lastly, you might want to make sure that your network Routers are not dropping pkts during those bursts because that will just be retransmitted packets which will only exacerbate your problem.