I'm running Ubuntu MATE 16.04 and I'm having trouble installing Kdenlive Version 15.08.1 on it. None of the icons are showing up on the program's interface.
Screenshot: https://i.imgur.com/Fjp0bNt.png
I've installed all the usual packages that people have recommended such as kde-runtime and the oxygen icons theme but to no success. There's also no useful information when running from the terminal. I'm stuck for ideas and could really use your help.

Try running QT_QPA_PLATFORMTHEME=kde kdenlive, do they show up then?

Thanks for the help there.

Interestingly enough, the problem has been rectified once I updated to the latest version of Kdenlive via the PPA.

There has been a Kdenlive bug fix recently that I think is related to the issue reported here; if I remember correctly, this fix forces the Breeze icon set on GTK desktop environments unless explicitly overwritten later from the Kdenlive menu. This is to ensure that people installing Kdenlive into a non-KF5 installation to have all required icons visible.