If you're having problems like that, it's probably a temporary issue with server or database load, which occurs relatively frequent in comparison to many others due to the sheer volume of users that pass through on a continuous basis.
It's worth bearing in mind that GUI images across LucasForums are actually hosted on a separate dedicated server to the forum itself for load reasons, and a potential outcome of heavy load hitting the server with the images can result in them not loading properly despite the forum itself seeming fine.
This can manifest in either the CSS styling images not appearing at all, or the images in your cache still loading but not those that aren't, the latter of which results in some images not loading and being replaced with the backup text (could be "?" depending on your browser).
All I can recommend is a refresh, and if it persists post a screenshot here and — more importantly — a dump of the source code so we can at least get a full understanding of the problem's symptoms (View > Source).