If you are talking about Object Dock, the backgrounds and themes (packaged background and icons, only useful if you have the same apps/games etc as the author has) are not resolution dependent, setting the icon size in OD config sets the size of all.
Some docks are put together differently, as in having outside border to move icons from edge but if icons size at 40 and dock has 10 border that is 50 pixels. That will be same 50 pixels (height when at top as example) at your 1920x1200 as at 800x600.