I am sure I can make the form non modifiable by using roles, but if there are users who are in multiple roles, how do we restrict the form to be read only an all cases. I just don't want to make each field read only. Wish there was a section based settings to achieve this.
"In any table where you want to use an image onload field (typically named [-]) create a text formula field with some HTML allowed using this formula"
What do you mean by [-]? What sort of field I create?
You can actually name the field anything you want and then arrange for the field on the form to have alternate label text selected but left blank. The reason [-] was chosen for the name is that if the field is used in a report it will take up the least amount of space.