I all but give up. The last suggestion: open a "text" file in CS5 and "save" or "save as". It may now be shown as an image icon. Another thought: when I save files in Photoshop, I then see them as image icons. Sometimes, when they get transferred from another computer, especially from a PC to a Mac, or e-mailed, they may lose the image, although still openable with Photoshop. Could be just a CS5 glitch or transfer glitch.
If they all open well, I would not be worried...

3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN