Hi there,

You can achieve that by going to Backend>Components>EasySocial>Profile Types>Type of Profiles>Default Pictures as shown http://prntscr.com/cw5hq7. You can follow steps in this Documentations for more references.

Can we add a default avatar based on user's gender ?

Unfortunately, currently we do not have this features yet . But it would be best if you can submit a feature request regarding this issues in our voice page -> http://stackideas.com/voices, so everyone else could vote for it, the more people request on this, and we will priority consider it.

EDITED