This is a very simple and problably have Hundreds of articles talking the same thing, but "Why not"
First create a "Document Library" , where you add your pictures.
After create, go to your webpart Page and start adding Listview "Document Library" WebPart and image WebPart.
To Webpart Connection Works, 1 WebPart have to be The Provider "Document Library" and other the consumer "Image WebPart" and we can start editing.
Edit "Picture" select "connections"->"Provide Row to"->"ImageWebPart", There you select Column "Document URL" and When you select a Row The picture will show....
One more thing, if you are using a custom List and have multiple attachments "Pictures", WebPart Connection Field "attachment" will not Work because is a "True/False" result, The workarround is you add a URL Column where you add the path to Image and then make The Webpart Connection.
Hope this help.