Are you puting the images in a Table? If so, the keep it the way it is and click the table itself. Then look at the bottom under properties. You should see a few settings for that table like, Border, CellPad, and CellSpace.
You can have the CellSpace anyway you want, it just gives the image or whatevers inside taht table some space and room. The Cell Pad gives it its outter lines look. Like how wide you want it to be. The Border is the part you need to change. it is probly set to 1. So change it to 0. This way, you shouldnt see any lines there at all.
When I put an image in a table, this is what I use....CellPad= ; Border=0; CellSpace=2
Try those settings as I am sure that would help you!