Hi Pablo Alejandre del Rio,
Thanks for contacting us and for your question.
The themes that you initially see after dragging a RadControl on your form are the default themes which are preloaded by our theming mechanism.
However, you can easily expand the variety of themes available by choosing them from the Toolbox and dragging them on your form, i.e. the rest of our themes are to be found in the Visual Studio Toolbox after your installation has completed successfully.
I hope this helps.
Do not hesitate to write back if you need further assistance.
All the best,
the Telerik team