Today the official Howard the Duck image was released in HD, I noticed something in the bottom left hand corner:
See it? I could only just make it out, so i screenshotted the part I wanted, changed the brightness in GIMP, and put it beside an Image of Man-Thing for comparison:
See it now? We're just going to have to wait for official confirmation now, but with this, Man-Things partner in Ironman 3 and Maria Hill saying "Who or what is a Man-Thing?" in Agents Of Shield, I think they might be hinting at something.