Deploying Wekan under a sub-path of a domain name was recently implemented in devel (see #133) and will be shipped in the next version of Wekan.

I strongly suspect this “avatar not displaying” bug comes from Collection-fs not taking into account the ROOT_URL environment variable correctly to support prefixed URLs. I will probably open a PR to support it (which should be fairly similar to the support introduced in Flow-Router in kadirahq/flow-router#329)