Evarcha,
If you have only recently worked with textures - that is an excellent job you should be proud to show off. If you like making textures, then you should make more of them and use them in your game - making it very original.
As a general rule all textures should be seamless. i.e. they should have a surface pattern that matches all around with the next repitition so that no joins are visible. There are a number of seamless tile making progs around that can at least be used to view what a repetitive texture will look like so you can adjudge the blending of each tiled repitition.
Harms Tile is quite good though I am not sure it is still free. Wally too can give you a tiled view and is a very useful program to have in any case.
As to this specific texture - there is nothing wrong with the pattern as is from the point of view of the pattern size and it could be used quite successfully in places such as single storey scifi type room walls or corridors where a metalic feel are required. As a single texture instance it could be used on a door entity. For use on walls in these circumstances I am not sure the two sides of the texture would be seamless so you might have to do a little work to make sure both sides end with exactly the same part of the texture so that they blend seamlessly. Just a matter of copying a small strip from one side, moving to the other and flipping horizotally and blend in if necessary.
Large patterns like this can indeed be successful in locations as I have mentioned as they only need be seamless on two sides. If you want to repeat the texture above or below then you will need make your textures match top and bottom too which this one does not.
The actual pattern can be any size and can depict anything at all you want if it fits in with any game design or plan you have, be innovative in your gamemaking and texturemaking.
Not all games or parts of a game call for your basic concrete, brick, grass and alike.
Of course if you are making textures you wish to give away to other FPSC users then they probably will.
There wont be many general users making an FPS looking for the kind of textures you see in a game like MDK - mores the pity.
I'm lovin it.