Rick,
"but I want to point out that the PNG file might be named MyGraph1.png instead of MyGraph.png. "
That is due to you have two destinations for ODS Graphic (ods html and ods html(2) ) ,
therefore MyGraph.png is for the first dest, MyGraph1.png is for the second dest .
And if you only want "MyGraph.png",you need close the first dest, Like this:

%let GPath=c:\temp\a ;

ods _all_ close;
ods html(2) gpath="&GPath./images" style=HTMLBlue;

You gonna see "MyGraph.png" instead of "MyGraph1.png" under "c:\temp\a" .