Most arrows point at something important. Perhaps The Arrow can be used to navigate, maybe it even points to 325
if North on the Dharma Oct symbol is where there are 3 openings (1:30 o' clock), then the arrow on it points to exactly 315 degrees, which is halfway between the 325 and 305 bearings used to get off and on the island with all three bearings falling within the top octile of all dharma octagons. Of the eight binary triplets on the octogon dharma logos, "1:30" is the only straight line. North is generally indicated on maps as a straight line. North is also generally indicated as bearing 000, which is the binary at 1:30. This supports the binary theory of the numbers.
Perhaps the arrow was some kind of armory, allowing DHARMA to study new forms of weapons and also used for a intelligence purpose.
The station the Tailies found wasn't the whole Arrow station. On the Blast Door Map, there is a small part that connects to the main station off to the left of it. This may be a supply station that the Tailies found. They also may have found one of the "CV's" on the map, seen clustered near The Swan and C4. This "CV V" (CV 5) may not be visible on the map, as the top is slightly cut off.
This may be supported by the fact that the station which the Tailies visited had a DHARMA symbol where the inner circle was a dotted line, while in other places the symbol has been seen with a full circle.
The station that they found may have been separated from the rest of the station like the source of the magnetism was covered up in the swan.
The Quarantine warning on the door supports theories that people lived in the Arrow and were not supposed to leave, much like the Swan.
From what the Tailies found, it is possible that most of The Arrow or The Arrow itself is simply a storage bunker. If that's the case, it may be possible that there are other "Arrows" on the island. The Arrow would be a collective name for all of them.
There's more to The Arrow than we think. The Swan and Flame both had trapdoors so what's to say The Arrow didn't have one concealed that leads into a larger area.
At the Comic Con 2007, in the Orchid Orientation Video it was said that no one can know what you do here, they only think this is a botanical research facility.
The Staff also had the hidden room that Juliette enters in "D.O.C."
Couldn't the eye belong to the person in the mural with there eye scratched out, I believe the arrow represents some sort of direction for salvation, through a person, probably Locke
As the station's purpose was to develop stategies against the Hostiles, it makes sense that after the Purge, the Hostiles cleared the station of anything that could be used against them, should DHARMA ever return to the Island. This may explain why the station is almost empty in 2004.
The Arrow got it's name from the fact that the Hostiles used arrows to attack intruders. The Arrow's name and logo are symbolic for DHARMA's countermeasure against the Hostiles.
The DHARMA logo on the wall of the Arrow was painted using a wooden mold with the necessary cut-outs. This logo needed to have the color of the inner circle inverted and have the circle interrupted, as it was hard to paint the standard logo on the wall with this technique. (It would have required unconnected character shapes, instead of simple character cut-outs to paint the name of the station in the logo) The Arrow logo on Horace's jumpsuit is the standard Arrow logo.
The "secret" piece of film of the Swan Orientation Video, which was hidden inside the bible is some sort of key to the island.
The arrow station could in fact be the cabin that Jacob resides in built by Horace Goodspeed, the arrow station shown in season 2 could be a decoy station for the real arrow.
Since Horace was building a cabin and worked at the Arrow, this could be the cabin he built and Locke's dream could have been a tiny bit off (or the island could have some how changed the map. Jacob and Horace's cabins could be completely diffrent. Also, If Horace built the cabin in the 70's, where would Jacob be in 1954, which Richard ovbiously knew when Locke said,"Jacob sent me." Although, Jacob could've been in the Temple or Richard is a time-traveler, but I doubt that, but that could be why Widmore still didn't trust John... no still doubt it....Jeez, I sound like Faraday with all these crazy theories in 1 paragraph!