Custom issue type icons not showing the correct size on some screens

Summary

Issue type with custom icons are showing bigger on some screens.

Steps to Reproduce

1. This issue can be seen on Custom fields > Click on Configure for any field > Edit configuration > Choose applicable issue types.
2. Depending on the issue types of a service desk project, the issue can also be view on Project settings > Request types.
3. Backlog of a Classic Scrum project.

AND

1. The custom issue type avatar is bigger on epic issue links (old issue view)
   

Expected Results

The icons show as a normal size.

Actual Results

Some system icons and also custom icons are bigger than the others.

Notes

There might be cases where the image is slightly bigger than the default ones, that might be because the default icons have a white margin, as you can see here

To work around this you can try replicating this white margin in your custom icons