If you are planning to create a web part that can retrieve and display a thumbnail of a random image from the picture library, then you have two options:
1) The images are stored as binary fields in the DOCS table inside the _SITE database. The field name is CONTENT. Simply connect to the database to retrieve the image. This is not the way I usually get stuff done in SPS.
2) I would suggest you access the images via the Sharepoint namespaces. Picture libraries store their image files in the same manner as document libraries store documents, so get a reference to the picture library as an SPList class and retrieve the image from the SPListItem.File property.
protected override void RenderWebPart(HtmlTextWriter output)
{
string url;
string caption;
string HTMLtext;
try
{
SPWeb mysite=SPControl.GetContextWeb(Context);
SPListCollection lists=mysite.Lists;
foreach (SPList list in lists)
{
if (list.Title.Equals(PicLib.ToString()))
{
SPListItemCollection items=list.Items;
int rndCount=items.Count;
if (rndCount > 0)
{
int intRandom=rIndex.Next(1,rndCount);
url= items[intRandom].File.Url;
caption=items[intRandom].File.Title;
HTMLtext= "some html text";
output.Write(HTMLtext);
}
else
{
output.Write("There is no picture in the selected picture library.");
}
}
}
}
catch(Exception e)
{
output.Write(SPEncode.HtmlEncode(e.Message.ToString()));
}
}