sorry I got the answer:
source: http://stackoverflow.com/questions/87753/resizing-an-image-without-losing-any-quality

//resize picture
//keeping quality
Bitmap bm = new Bitmap("something.png");
Bitmap newImage = new Bitmap(100, 100);
using (Graphics gr = Graphics.FromImage(newImage))
{
gr.SmoothingMode = SmoothingMode.HighQuality;
gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
gr.PixelOffsetMode = PixelOffsetMode.HighQuality;
gr.DrawImage(bm, new Rectangle(0, 0, 100, 100));
}

//set picture for backgournd
NImageFillStyle imageFill = new NImageFillStyle(newImage);

imageFill.TextureMappingStyle.MapLayout = MapLayout.Centered;
m_Chart.Wall(ChartWallType.Back).FillStyle = imageFill;

nChartControl1.Refresh();

Thank you, It works as a charm.
I just have one more question. Is it possible to resize the picture as well?

Thank you,
Daniel

Hi Daniel,

Yes - you can use the following code:

NImageFillStyle imageFill = new NImageFillStyle("c:\\temp\\maplayout.png");
imageFill.TextureMappingStyle.MapLayout = MapLayout.Centered;
chart.Wall(ChartWallType.Back).FillStyle = imageFill;

More information on texture mapping can be found here:
http://helpdotnetvision.nevron.com/Presentation_Graphics_AppearanceStyles_FillStyles_Texture_Mapping_Style.html

Best Regards,
Nevron Support Team

Hi,

I am just wondering if it is possible to center an image for graph background instead of setting it to stretch?

I know I can set the background the way like that:

NImageFillStyle imageFillStyle = new NImageFillStyle("image path");

m_Chart.Wall(ChartWallType.Back).FillStyle = imageFillStyle;
m_Chart.Wall(ChartWallType.Left).FillStyle = imageFillStyle;
m_Chart.Wall(ChartWallType.Floor).FillStyle = imageFillStyle;

But that always re-sizes the picture.

Thank you,
Daniel