GTK application issues

[irenicus2015]

So I've been having some issues with a few applications, first in the list is pcmanfm file manager.

When I try to use the open_with option from the context menu (after right clicking a file) I'm not able to select any application.

http://i.imgur.com/glk27L2.png


Similar issue also pops up for example when using the app lxappearance nothing shows up in the icons section although I have installed some mouse icons from the repo.

http://i.imgur.com/Alx25wQ.png

I'm using i3 window manager, and have no other external desktop environments like gnome installed.

Sorry if the problem seems too obvious but I personally don't seem to have any clue about what the root cause of the problem is or how to get it fixed.

Thanks.