The basal enantiornithe Iberomeronis resting on the spike of a Polacanthus.
I think this is the first time I depict an avian dinosaur in detail and it has been a real challenge; I had to use at least half a dozen of extant bird pics as a reference to achieve something as simple as the wings folding position. It has been fun though, so more extinct aves are probably coming up soon.
In many cases it would just be a little stub (e.g.: Matt's restoration of Boluochia). Some species had one or more pairs of ribbon tail feathers like Confuciusornis.