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;
}
4. Save changes.
Screenshots
Without code
With code