Well, I formerly lived and worked in that area and I can tell you that there will be so many opportunities for pics that you will have to sort out the mediocre ones. You may, at this time of the year, catch the fall yellows from the Quaking Aspen, too, if the fall is right. The trip over the Beartooths is, to be sure, spectacular and get a picture of Pilot and Index peaks. If you had time, you could visit the Grasshopper Glacier, too.
Try to get off the beaten paths, too. One reason is that all of the easy shots are now beautiful, but a little trite. BTW, much of the Park closes on Labor Day, as that is the official end of the tourist season. The park may be open in spots and not open in spots by the time you get there, you just will have to see.