Short Answer: Unfortunately the User Profile Plugin can not affect the size of the profile pictures.
Detailed Answer: Larger profile pictures are a highly wanted feature request for Confluence - see also CONF-9375. They would make Confluence more social: Users will recognize other users in the system just by their profile picture.
The User Profile Plugin uses the profile pictures that are provided by Confluence. During the upload of a profile picture Confluence limits its size to 48x48 pixels. Due to that limitation we can not use larger profile pictures in the User Profile Plugin - although we would like to! (Stretching the existing pictures is not an option - they will become fuzzy and grainy)
Atlassian provides free licenses for non-profit organizations (further information). If you have such a license we'll give you a free license for the User Profile Plugin. Please mail us at mailto:confluence-support@communardo.de with the following information:
- a proof that Atlassian accepted you as a non-profit organization
- the Server ID of your Confluence
- the version of your Confluence
- the number of users your Confluence is licensed for
Similar to Atlassians rules this applies also for Open Source Projects and Classrooms. Qualified academic institutions receive a 50% discount on licenses.