In Moodle 1.8 I added a database activity to a course and I added a picture field to the only table with parameters: Width in single view = 100, Height in single view = 100, Width in list view = 100, Height in list view = 100.
I added a record with a picture and I went to see it in "list" and "single" views.
What I found is that the same picture is shown in two diferent ways.
One is resized, one is stretched.
Look at the attachment.