I have a linux desktop that uses Openbox and GTK2. I installed abiword, because honestly, I don't use Libreoffice Impress, etc. at all. I just use a word processor. Anyway, I installed Abiword and opened it, and I noticed that Abiword wasn't using my selected gtk2 theme.
Here's a picture of Abiword:
And here's a picture of a correctly working application: