The box effect is a nice touch, but I think the rather random mix of colours ruin it. From orange to grey to blue (ish) really doesn't work for me. Getting into the technical bits, you need to work on the overall composition. For instance, you really shouldn't cover up the main focal so much with effects. Let some of it shine through and be seen. Other things would be the position of the render. Take a look at the
You must login or register to view this content. (just read the top section, no need to read it all) to see how a render should be positioned. You do have decent text which is good as a lot of people struggle with it.
Overall it's nothing outstanding but it is a good start. Judging by this sig you do have potential to be a great artist if you keep at it and learn from your mistakes. As with everybody it will take time to get there, but keep it up and you will.