If you ever run into the following behavior :

Create the Mysite under a managed path , say http://myserver:90/sites/Mysites 

Define the above address as a mysitehost.

 

When uploading the pictures , the thumbnail is displayed as an red X

Going to the properties of the thumbnail, you notice the URL is malformed :

http://myserver:90/sites/mysitesUser%20Photos/ProfilePictures/DOMAIN_ImgUser_MThumb.jpg 

 

Until the behavior is changed, all you need to do is to go to the MysiteHost configuration page and add a trailing slash to the  URL:

http://myserver:90/sites/Mysites should become http://myserver:90/sites/Mysites/

Depending on the configuration, a reimport of the profile pictures might be needed (plus powershell cmdlet to create the thumbnails where needed).

Update-SPProfilePhotostore –CreateThumbnailsForImportedPhotos 1 -MySiteHostlocation http://myserver:90/sites/Mysites/