picture merge & overlay grid

Can anybody guide me to a solution for following problem: I need to make a big street map of our city, but only display a small part of it, it should be center to the last mouse position, by refreshing (a click on the map) and it should have a variable counter over the map. E.g., the map has 1000x1000 small pictures, which are put together to one picture of each just 10x10 small pictures. Info of some points are taken out of a database and showed in this 10x10 picture, whereby the database teach where exactly the information may be to put. The information can be bigger than one picture only. I need therefore to put first the picture of 10x10 together and overlay it with the database figures. Any help is appreaciated, e.g, how to put together the picture of 10x10 small pictures (with gd1.4) and how to overlay information on this new picture. bye Ronald