If the rendering controls of ILNumerics are not loaded from a regular application, you will have to give a hint, in order to distinguish regular rendering from design time behavior. Frameworks, which load the library dynamically at runtime (VSTO, devenv, LinqPad and obviously MEF) may cause ILNumerics controls to 'think' to be used in a designer. Hence the design time replacement ('circle') you found.
In order to make ILNumerics render the 'runtime way' instead, add the following setting to your app.config:
key="ILNIsHosted" value="true"
In the context of the app.config settings file:
<configuration>
<appSettings>
<add key="ILNIsHosted" value="true"/>
</appSettings>
</configuration>
The use of the app.config enables the application of the setting even in those scenarios, where the framework does not allow user code to be executed before the setup of any control. If your framework provides some initialization hook, you may just as well do the configuration by code:
ILNumerics.Settings.IsHosted = true;
Keep in mind, that this code needs to be executed early in the application setup. At latest before ILPanel is initialized. Otherwise, the use of app.config is recommended.