As someone who has been using the internet since the late 1990s, I disagree with the distrust of users who have an icon of a character, religious figure, flowers, etc. In the old days, many communities had a taboo about using your real face as your avatar/icon/profile picture. Some of us are set in those old ways or some simply don't feel comfortable showing their faces online. In fact, the highest rated seller of household goods bundles in my area only has a few cleaning brands as her icon and I've purchased from her without issue.
Some people value their privacy. Some people are dealing with stalkers who follow them, some times for years, across different platforms. Some people have severe body dysmorphia issues. And some girls fear that putting a flattering photo of themselves up may attract creeps who only want to use OU as a dating service and start accosting them in private.
There are many different reasons as to why someone chooses not to use their real face online and most of the time it isn't insidious.
Although you have a point in your logic about people not using their profile pic there is also the subject that some people do not put one up for sketchy reasons. In my area there are people who sells computer and laptops. Several have pictures of a kitten/dog with over 100+ sales but below 5 ratings. What that tells me is he/she doesn't give ratings to the buyer so that he/she cannot be given ratings on the items being sold. I have messaged this person for 3 laptops and she has read it but not responded. However, I asked my friends who also use offerup (not verified, semi-new to the site) to message her and she responds almost right away. I can only arrive to one conclusion, the user is not selling to verified and savvy users on offerup but more likely takes advantage of new users seeing as they won't take precautionary measures and knowing that is an item is exchanged person to person, the buyer will never see their money back.