When you place the GPS tracks module, all starting points of GPS tracks are shown. The standard google marker is used to show these starting points. I have made some changes to the php files so I can use different markers. How this looks can be seen on my site: http://www.gpscyclingtracks.net/kaart

Is it possible to add this as a new feature for categories. Ideally I would like to define the markers and assign them when I define a new category or change it for existing categories. 

It helps me in personalizing my site and show visitors waht kind of track they can expect.

Since the change to V4 included a database change and different table for the categories, it is not very simple to upgrade to a new version for me.