I mount a lot of flat screens and more often than not the cables are not considered until after the fact.
Disguising the cables can be easy enough with a strategically placed vase but a more permanent solution is often desirable.
There are some conduit systems on the market that hide USB and power leads inside aluminium or plastic tubing which is then attached to the outside of the wall between the television and the skirting boards, but nothing beats making the cables disappear altogether.
A local Sydney electrician can install an outlet for the power behind where the flat screen will be mounted but this still leaves the problem of the other leads being seen.
For a brick wall I use a 38mm core drill bit to drill a hole behind the flat screen where it won't be seen and another one just above floor level and then if the cavity is wide enough between the outside course of bricks and the inside, I simply feed a piece of strapping tape or the tongue out of a length of particle board flooring through the top hole and out of the bottom hole then tape my cables onto the end and pull them through.
In this case I was hiding the cables in a common wall which was adjoining to next door and the cavity between the two courses of bricks was only about 10mm so I had to use a diamond wheel on my grinder and a cold chisel to chase a groove for a length of 35mm PVC pipe to sit in.
After feeding the leads through the pipe I used some masonry nails to hold the pipe in place then I applied bondcrete to the brick and PVC surfaces and re-rendered the section of wall.
Of course if you are dealing with plaster board the process is much the same.
The only obstacle might be a noggin in the way in which case it may be necessary to remove a larger section of the wall and drill a big enough hole through the noggin to feed the cables through.
No matter what your walls are made of, I can hang your tv and hide the cables from view too!