according to MSDN documetation, in IE5 and above, IMG tag support WMF files (http://msdn.microsoft.com/workshop/author/dhtml/reference/objects/img.asp?frame=true):
The following image and video file formats are supported as of Internet Explorer 5.
.avi—Audio-Visual Interleaved (AVI)
.bmp—Windows Bitmap (BMP)
.emf—Windows Enhanced Metafile (EMF)
.gif—Graphics Interchange Format (GIF)
.jpg, .jpeg—Joint Photographic Experts Group (JPEG)
.mov—Apple QuickTime Movie (MOV)
.mpg, .mpeg—Motion Picture Experts Group (MPEG)
.png—Portable Network Graphics (PNG)
.wmf—Windows Metafile (WMF)
.xbm—X Bitmap (XBM)
or use the image control in isctrls.ocx, for example: