Not sure if you are running the same version as I am but in 2005, you go to the details tab on the inventory master.In the lower right hand corner there is a camera. You click on this then point to your picture file.
Hope this works for you.
We installed R/3 in Fall of 2004. I am referring to a MM02 screen. I don't see a tab called details.
You are not in the right discussion forum. This is only SAP Business One products. I have worked on R/3 in the past but I did not use loading pictures to the Material Master. You need to find the SAP R/3 or MySAP discussion forum.