Answer
No, an ArcGIS schematic generated by the ArcGIS Schematics extension cannot be published with ArcIMS 9.1. The ArcIMS ArcMap Server feature does not support ArcGIS extensions, so MXDs cannot be used. Schematics cannot be directly read by an axl.
Export the schematic as a shapefile and then publish it with an ArcIMS map service via an .axl or .mxd map configuration file.