Picture controls can contain images in the following formats:
Bitmaps, with .BMP or .RLE extensions
Windows metafiles, with the .WMF extension
GIF or animated GIF files, with the .GIF extension
JPEG files, with .JPEG or .JPG extensions
You can create the image in another application or use a scanner to create it.
PB帮助里面说的, 也就是上面的这几种格式 BMP RLE WMF GIF JPEG JPG这几种