It's easy. Use Mapped Folders in Visual Studio 2010. Right click solution name and select Add > SharePoint "Images" Mapped Folder. This will add Images folder to your solution. Images folder will have one subfolder named on your project. Add your images to this folder (You can drag and drop them if they are already in your project). That's it. Build and deploy project. Images will get copied to the _layouts (inside project folder) folder.
Read following MSDN article for step by step detail:
http://msdn.microsoft.com/en-us/library/ee231521(VS.100).aspx
Read following MSDN article for step by step detail:
http://msdn.microsoft.com/en-us/library/ee231521(VS.100).aspx
