Thanks for contacting us. This is a known limitation of the RadForm
Title Bar which will be addressed in the new release of RadControls
scheduled for the end of this month. We will provide the possibility for the user to change these images by modifying the theme of the Title Bar and using predefined states (Form Maximized, Form Restored etc.) to adjust the images for the appropriate state. You can write anytime you have further questions or feedback.
the Telerik team