The ornamental design for shower curtain holder, as shown and described.
FIG. 1 is a perspective view of a shower curtain holder showing my new
design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a side elevational view thereof; and
FIG. 4 is an end elevational view thereof.
The side and end opposite to those shown in FIGS. 3 and 4 are substantially
mirror images thereof, and the bottom of the holder is substantially flat
and unornamented.