You are right that the i.MX7 does not offer a GPU or other multimedia releated HW acceleration. However some basic low resolution video stuff should still be possible.
In the first demo image we likely installed some plugins which do not work on the i.MX7 so maybe if you use one of the ‘auto’ plugins the constructed pipeline is not compatible with the i.MX 7 hardware.
That said the following does work for me:
gst-launch-1.0 videotestsrc ! ximagesink
gst-launch-1.0 videotestsrc ! autovideosink
gst-launch-1.0 filesrc location=~/file.mp3 ! id3demux ! beepdec ! alsasink