There are, in fact, about 4-6 different Orc appearances available to PCs, but they are automatically set upon the first login based upon class and gender. Your complaint is not a new one, nor is it unique to Orcs. Half-giants and half-ogre characters also had the issue of a single appearance for many years, though we eventually integrated a dynamic model for half-giants. The unfortunate truth is that we do not have a "dynamic" orc appearance (meaning one where the various parts of the model can be tweaked), so we make do with what we have.
It has long been, and continues to be, that players who truly wish to play monstrous races, be they orcs, goblins or even dark elves, need to be prepared and accepting of everything that goes along with them. Key among them, people (the general population of the world) will look at you and fear you. To them, you look like any other orc or goblin. Goblins do have some more dynamic options, including a small number of heads from which to choose.
Another problem I have with using a half-orc skin for an orc PC is that people (other players) who don't look up such a character in LORE or the character submission or already know about the character will just see a half-orc, not an orc. People should see an orc, ugly and drooling and yes, somewhat terrible. They should see a creature that is generally shunned by all civilized people. Half-orcs, while still not exactly pretty, are more accepted (though not universally so).
Having said all this, there is precedent for people requesting a change to the half-orc appearance for their orc PCs. I don't like it personally, but it is an available option for those who feel the need to have a customizable orc. This is a request that can be made after the character has been created and appears in-game. We can't do anything about the relative size of the creature model, however.
