Well since this is your first I be gentle MUHAHAHA

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first thing is the color, that blue is way to bright especially on a white background, I would suggest either make hte blue a bit darker or turn he white background into a darker color. Reason is your want contrasting colors like dark on ligh or light on dark, so as to keep them seperated but also show a little blend to them.
Next thin is the scan lines you don't want to cover the whole thing with them, reason being, when its time to cut you could have some problems line them up (thats if you convert the tables to divs) and also it removes any depth you would put into the rest of the design. So what I would recommend is that you just have your background with the scanlines and your content tables all solid or vice a versa; it's the same thing with contrasting colors you want them to be distinguish but be able to flow with each other.
Next recommendation I would do is work on using drop shadows as they give a flat design look more 3-d'ish if you can think about it that way, especially if your using a light background such as white, since drop shadow give a small separation to the design and the background. With the circles drop shadow would look nice, I would recommend looking up tutorials that deal with glass orbs and such to help spruce them up.
Overall it's ok, keep working at it, from time to time when I make it a template I usually spend all day tweak this or tweak that to give it a bit more.
I would hit up pixel2life.com as they have quite a few tutorials on building websites from adobe, you can find some good idea's to help along the way.