By default, the theme/platform does not have this option and currently, the BuddyBoss Theme overrides the thumbnail size to make sure to have a consistent layout. You can use the following CSS code.

Please follow the steps below:

1. Go to BuddyBoss > Theme Options

2. Under Custom Codes, enable CSS

3. Append the following:

#buddypress .users-header .gamipress-buddypress-points span.activity,
#buddypress .users-header .gamipress-buddypress-achievement-thumbnail{
    width: 64px;
}

Note: You may change "64px" to your desired size.

4. Save changes.

Note: Any modifications are considered as custom work already. Know more about our Support policy here: https://www.buddyboss.com/support-policy/

Screenshots

Without code

With code