Hi, Andreas,

To set an image to a cell you can use the CellFormatting event of RadGridView.

void radGridView1_CellFormatting(object sender, Telerik.WinControls.UI.CellFormattingEventArgs e)
{
    if (e.RowIndex == count - 1 && e.ColumnIndex == header)
    {
        e.CellElement.Image = new Bitmap(Resources.test);
    }
    else
    {
        e.CellElement.ResetValue(LightVisualElement.ImageProperty, Telerik.WinControls.ValueResetFlags.Local);
    }
}

For more information about formatting cells visit our help article: https://docs.telerik.com/devtools/winforms/controls/gridview/cells/formatting-cells

If you have a whole column with images I recommend using an image column: https://docs.telerik.com/devtools/winforms/controls/gridview/columns/column-types/gridviewimagecolumn

Additionally, if you want to set header cells image, refer to the following help article: https://docs.telerik.com/devtools/winforms/controls/gridview/styling-and-appearance/images

Let me know if I can assist you further.

Regards,
Todor Vyagov
Progress Telerik