Does someone know if there are Options to fundamentally change the layout of the IRFs (eg. to multi-column layout, background image etc) ?
The forms are not that configurable. I do believe that you could create different columns, but you cannot alter or configure an image for the background.
This would make a good IDEA for an enhancement to a future version of the software.
When I need to create a fully-customized form, I usually just create a webpage (in my case in ASPX) and then call CAPA via a webservice and pass the values that I need to start the job.
Not only does it load a lot faster than an IRF, I can capture the user's credentials, and don't have to give them access to CAPA itself (since it usually isn't required).
Plus you can customize it to your heart's content, and make the page blend in with your normal intranet's look if you want, so the users don't even notice the difference.