I (and I know its not just me) have found it annoying that there is only one sign, which is wooden. When making maps or builds it can be annoying, since the sign doesnt fit in with its surroundings. Ex: Making a Tauredain temple but an oak wood sign takes away from the color scheme. My idea was that each faction (Probably not Hobbits) will have their own sign, similar to how each has a gate. So for example, a Gondor Sign would be gondor brick design or something similar that fits. The only sign that wouldn't work very well would be Mordor sign, since black writing on black signs would be hard to read. Instead, the Mordor sign would most likely be Charred Wood.
If making all the signs look like faction bricks would be too difficult, then it could just be the types of wood, as most factions have wood that are associated with them. (Ex: Gondor has Lebethron, Hobbits with Shire wood, Dunland with Spruce wood, Harad with Date wood, Mordor with Charred Wood, etc)
Edit: There should also be Ithildin writing for dwarf signs, unless that is already planned (I havent seen it on the planned features list)