The ornamental design for shower rod mounting bracket, as shown and described.
FIG. 1 is a perspective view of a shower rod mounting bracket in accordance with the present design;
FIG. 2 is a front perspective view thereof;
FIG. 3 is a rear perspective view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a front view thereof;
FIG. 7 is a rear view thereof;
FIG. 8 is a left side view thereof; and,
FIG. 9 is a right side view thereof.
The broken lines showing the shower rods, ring bracket and wall in FIG. 1 depict unclaimed environmental subject matter and form no part of the claimed design.