If a tower shield is used to provide total cover as a wall does anyone standing behind the person using the tower shield also have cover from an attack such as a dragons breath weapon? Would there be an area of total concealment spreading out in a "V" with the tower shield at the tip?
You already provide cover in that shape by virtue of occupying the square:
Creatures, even your enemies, can provide you with cover against ranged attacks, giving you a +4 bonus to AC. However, such soft cover provides no bonus on Reflex saves, nor does soft cover allow you to make a Hide check.
Unfortunately, this 'soft cover' applies only to ranged attacks and not to reflex saves, so the dragon's breath will burn your allies nonetheless. The tower shield may contribute to the soft cover you do grant, however:
In some cases, cover may provide a greater bonus to AC and Reflex saves. In such situations the normal cover bonuses to AC and Reflex saves can be doubled (to +8 and +4, respectively). A creature with this improved cover effectively gains improved evasion against any attack to which the Reflex save bonus applies. Furthermore, improved cover provides a +10 bonus on Hide checks.
Note that, because the improved cover granted by the shield's use would still be improved soft cover, you will not benefit from the improved evasion nor the bonus to Reflex saves. You do get the bonus to Hide checks by the RAW (soft cover merely does not allow you to make hide checks on its own), but that might well be taken away from you by GM fiat.
That said, you do NOT grant total cover or any kind of concealment to anyone besides yourself.
The tower shield entry says
In most situations, it provides the indicated shield bonus to your AC. However, you can instead use it as total cover, though you must give up your attacks to do so.
You gain total cover, from all attacks (though not from targeted spells), in all directions. Only you.
This cover doesn't spread behind the shield, partially because there's no facing in regular D&D 3.5.
(This question is closely related)
RAW: No, but your DM may rule otherwise
The rules as written would say no, based on Chemus's answer, but taking cover from a dragon's breath attack is the kind of thing that a DM might rule as okay because it makes sense realistically, if not mechanically.