Source: http://lifehacker.com/upload-anything-to-flickrs-new-1tb-of-space-with-a-sim-510138485
Recently, Flickr gave all of its users 1 terabyte of free space. Reddit user rlaw68 shows how to utilize that space for more than just photos and videos.
The process involves combining the file you want to upload with a gif. Flickr checks the headers of the file and sees a picture and grabs the whole thing. Unbeknownst to the server, though, your file is tagging along in a makeshift zip package. As per rlaw68's instructions:
So, how to do this:
1) Put the two files you want to combine into a single folder, preferably off the root of your drive, say c:\combos
2) Hit the Windows key + R, type in CMD and hit Enter
3) Change the directory to the root:
C:\users\Bill>cd \
4) And then to the folder where your files are:
C:>cd combos
5) Now, to combine the files type:
C:\combos>copy /B project1.zip+cat.gif project1.gif
6) That’s it! Now you’ll see a file called project1.gif in your \combos folder that you can upload and store on Flickr – it’ll appear as just whatever the .gif file was that you combined with your archive.
When you want to access it again, you just download the file, rename it with a .zip extension and open it like normal. If you're using a Mac, WonderHowTo also has a primer on how to accomplish this task.
This may not be useful for most situations. Flickr has an upload limit on photos of 200MB, and this process means that it's somewhat cumbersome for daily use instead of a service like Dropbox, but in a pinch, it never hurts to have a backup plan. While it won't work for uploading to Flickr, you can also hide files in a JPEG
How to use that 1TB of free Flickr space to store stuff other than images | Reddit via WonderHowTo