A fellow member - :Eatsith: has told me that the method of adding deviations to the Featured folder in the group has a problem.
Here's the easy way to add stuff from your own gallery to the group:
* Click the Gallery tab to go to the group gallery.
* In the upper right, click the button Submit to this gallery
* Two options will appear:
* * Submit a new deviation... This will take you to the screen to upload a piece, just like if you were adding new art to your own gallery.
* * Contribute an existing deviation This option opens a menu where you can add images from your personal gallery to the group. This is the easiest way to contribute artwork.
I hope that DA will make a better group system soon!