Sounds like you might be missing monster sprites, or have outdated/incorrect LUA files for your client. Make sure that your kRO installation is fully updated and that your LUA files are current to your client version.
Where are your LUA files located (data folder, GRF)? If they're located in your data folder, is your client diffed to read from the data folder first? I'll test out a 2013-03-20 client later tonight.