The five icons under each thumbnail in your archive correspond to LightRocket’s five recommended file information (or metadata) fields. These are description (including the who, what and why of your picture), keywords, credit/copyright info, location info (at least the country where the picture was taken) and the date the picture was created (at least the year).
You’ll notice that some of these icons may have been replaced by green ticks. A green tick indicates the corresponding recommended file information field is complete. The presence of a visible icon indicates it is incomplete.
So when you see a thumbnail with icons under it, this means some of the recommended file information fields are empty. A thumbnail that is ‘ready’ for publishing live on yours and the LightRocket site should have a nice row of green ticks under it.
You can also review your file information by rolling your mouse over these icons. You can even edit the corresponding file information field by clicking on the icon or the green tick.