Tricky. The traditional approach is featured articles but it is unlikely one could be created in time.

Might be able to get something like

https://en.wikipedia.org/wiki/File:Dendrogramma_enigmatica_sp._nov.,_holotype.png

or

https://en.wikipedia.org/wiki/File:Multiple_Dendrogramma.png

Through featured pictures mind.

A talk on what open access journals are out there that wikipedians could cite might be of interest (PLOS one is great but it isn't my field).