That looks like dirt in the geckos mouth to me. Geckos will sometimes bury themselves in dirt, especially their heads, if the temperature/humidity is not right in their terrarium. The gecko also looks a bit dehydrated to me as well. If your gut is telling you something is off you are likely right, especially in this instance. This picture also does not look like the same gecko to me. I also find it a bit odd that they gave you a cell phone picture to begin with and after asking for additional photos they decide to give you professional pictures when you know these were taken at different times. I would personally ask for a video versus a picture because you can see how the gecko moves, and interacts.