Which Chrome browser version you're using exactly?
So I just went around reading about the issue (of which I also experienced too), and realized it appears to be fixed already, at least for me.
To confirm again, I also quickly pulled my phone and tried viewing images on Facebook via Chrome, and they appeared nicely, not in small size.
Assuming the issue (which is likely a CSS issue) was reported some months ago, I am sure they'll be at it and tried to fix it.
My images appear alright though. Perhaps update to the latest Chrome on phone and it might solve it for you. I didn't even noticed it's been fixed until reading this question and going to explicitly try it out.
As a proof, see image attached. This is how images show on my Chrome when I visit Facebook for mobile, the
FWIW, my Chrome version is 42.0.23311.bla-bla-bla. I'm on Android 5.1.1, custom build, using CyanogenMod for Xperia Z2