Would it work using Time Capsule both as Time Machine AND media container? I currently have a Macbook Pro and Time Capsule 3TB (ac-wifi).

The easiest solution for me would be to use the TC for both media storage AND backups via Time Machine. 

Would this be possible?

I am thinking that the system could be "confused" loading down photos from TC to Macbook, and at the same time making backups with those same files from Macbook to TC. 

I also read that OS X Photos and similar don't work well with external drives.

Can someone please bring light to this subject for me?

Thanks!
You can setup your AirPort Time Capsule to be a file server.  Just create several folders or as you require.  Use port forwarding in the Airport side to forward your WAN or internet connection to the Time Capsule side.  Use DynDNS to setup an account and then connect from anywhere in the world where the internet is not censored.  You will want excellent security configured for the AP Time Capsule if you go this route.

Or you can just use the Back to Mac function that is available through iCloud and is native to OS X.