Add a button (or set a field), to open a pop-up when this is clicked
In pop-up we can see a window as this:
[login to view URL]
(this plugin is for example but if you know other opensource solution is the same)
with this plugin we can wrote in two display Area:
Signature Technical:
Signature Customer:
At the end of this operation (technical and custumer are sign two related area) click button to return on vtiger; and in this moments two image generate from plugin have to put in ticket, (there are already two field image to save this two image provide to plugin)