Note that not all versions of Ipe are capable to show the bitmap. If Ipe was not able to allocate enough colors to show the bitmap, it will simply show a stippled rectangle.
You might be tempted to use the bitmap object type to include some logo or the like into your drawings or slides. However, for that purpose you should consider whether it is not wiser to use the LaTeX epsf.sty package. If you make a text object with contents
then the bitmap (assumed in encapsulated Postscript format) will be included only when printing, keeping your Ipe files small. And if you have Latex Boxes on, then you can even see a real-size bounding box for the included file. Just don't forget to add\epsfbox{logo.eps}
\usepackage{epsf}
to your LaTeX
preamble.