I like the overall design of it but if you are making this in order to later develop into a website you need to be aware of the way CSS works and also how to make your website load in the quickest possible time.

With CSS you can off centre things but necessarily working in thirds is the best way to make sure your final web design will match your primary idea.
One thing I seen you doing wrong unless you really wanted it unaligned was the whole alignment of everything, In Photoshop you NEED to use the align tools all the time if you aim to make a website that doesn't look slightly off and in the long run it makes coding the stylesheet much easier .

Another thing I spotted was the background noise, the way you've added noise to the background would hammer loading times as you cant add that pattern to the stylesheet. Gaussian noise is completely random which in turn if you did cut and use you would end up with merge lines and offset pixels.
The way you should of done it unless you didn't want to, Would be to create a noise pattern in a set amount of pixels then filled the area with that pattern. Then later in the coding stand point all you would have to do is take that little set square of noise that is tillable and tile it over the gradient box you made.


Other than all that It looks more than fine
Keep making the web designs or even take it a step further and try and code a mock-up of one of your designs and keep the file-size to an absolute minimum.

Nice stuff Bap