I was trying to upload images to a Pictures Library, and getting thumbnailing working, and so on. I found that thumbnailing wasn’t working, so I kept trying to create and upload my own thumbnail, which was pretty dumb. SharePoint will do that for you – but you’ve got to upload your file with a correct extension for an image format…
The code that worked was:
SPPictureLibrary pics = (SPPictureLibrary)site.Lists["Pictures"];
FileStream fs = new FileStream(@"c:lolrus.jpg",FileMode.Open,FileAccess.Read);
pics.RootFolder.Files.Add("lolrus.jpg", fs);
Previously I’d been trying this for the final line:
pics.RootFolder.Files.Add("lolrus", fs);
The thumbnails weren’t being generated because I failed to have the .jpg extension. I guess I figured I was defining the Display Name of the item, rather than the file name. I added in the ‘.jpg’ and when I uploaded my image, thumbnails were automatically generated. Nice.
Andy Burns' Blog 
Good concept in article….
Nice to go through…if possible elaborate so that new to MOSS people can understand easily…
Thanks
Not really a lot more to say. Create yourselve an SPWeb object, then get your Picture library as above (“site” is an SPWeb object).
This article describes getting an SPWeb object:
http://www.novolocus.com/2008/11/14/how-to-get-an-spweb-object-from-a-url/
You’ll need to reference and use the Microsoft.SharePoint assembly – so this code will only run on the server 😦 If you need it to work remotely, well, you’re looking at having to use web services then.