i have many suggestions, but i can see you don't have a lot of experience with design so i will list the most obvious to not confuse you. aside from that you need to learn some basic photoshop techniques:
the background should never be a grid-like repeating pattern. the hard outlines on around your design does not work. the bevels for the top part that looks like it is for navigation are too plain looking.
what really distracts from your design is there is too much empty space between your 'tables'. emtpy spce is good if used right, i can't explain why, it just does not work in this case.
the header and thumbnails look okay. oh hey.... i think i can explain it a bit now: you are trying to mix 3Dish with 2D design, this almost never works well. example your thumbnails are 2D but you have bevels all over the place. also it is that your bevels are plain. hope this wasn't too confusing and helped you a bit.