We have created a portlet. We then went through some pain to move images from our portlet into a theme created for our portal vendor. I disagreed with this move, thinking that having application images within the theme overstepped the bounds of the theme. We are now having issues caused by having the images in the theme rather than the portlet. A good part of that is because of our implementation, but I believe a portion of those problems are simply because the theme shouldn't contain application images.
Having said that, if you look at themes for the firefox browser, they override the images within the action bar, like the home, back, refresh buttons. Of course, one large difference there is that firefox is an application, not a web application, but does that really make a difference in where a theme should begin and end?
I'm not a web-ui guru, and would like some input from the community on guidelines for what is appropriate in a theme and what should remain part of the web application, and why.
My initial take is that application images (those that are a part of application presentation, and would be particular to a single application) should be part of the application, and layout, color schemes, and fonts should be part of the theme. If that's the case, how can you make an application that includes application images look good in themes with vastly different color schemes?
Our environment is Liferay portal, so it could be that the image handling within themes in liferay is different than other systems, but I would be interested in examples from other systems as well.