How large is the MY.PICTURE file?  If it is about 8K then it is a
standard HiRes picture.  If it is about 16K then it is a Double-HiRes
picture.  Since you see it after using PR#3 and you said you created 
it with MousePaint then it is probably Double-HiRes.

There is no standard file format for Double-HiRes pictures.  Such
pictures are loaded in both the standard memory and aux memory
banks on an Apple IIe or IIc, half in each.

Here is a simple program to prove to yourself that the HiRes
screens work okay:

 10 NORMAL:TEXT:HOME
 20 HGR:HCOLOR=3
 30 HPLOT 0,0 TO 279,0 TO 279,191 TO 0,191 TO 0,0 TO 279,191
 40 HPLOT 279,0 TO 0,191
 50 PRINT CHR$(4);"BSAVE HGR.PICTURE,A$2000,L$1FF8"
 60 GET T$
 70 HGR2
 80 PRINT CHR$(4);"BLOAD HGR.PICTURE,A$4000"

--
Paul R. Santa-Maria
Monroe, Michigan USA