This is an adaptation of the icon theme for Pidgin known as "iPhone". It was originally created by Hernou. His Github for this item can be found here:
I upscaled his images and modified/added a few to fit Gajim.
Install in the standard Gajim folders (Linux should be under ~/.local/Gajim/iconsets or similar, Windows will be in C:Program FilesGajimdataiconsets)
Please leave a comment if you feel that this could be improved somehow. This is my first gnome-looks submission, so I don't know what the community prefers yet!