> Can the banner be around 500~ width?
If you like! The width limit was largely to keep some people from overextending themselves, but also in the interest of making it fit on most people's browsers without having to scroll. Keep it under 1000!
I made a banner for the competition, but I'm not too happy with how it turned out. I'll post it anyway, I guess.
It's a very good start! I gave you guys lots of time for a reason, you should all be posting your WIPs and asking for advice! Only the end product will be judged.
Your highlights are very nice but the overall shading job isn't so great. The banding on the empty vat on the left is particularly egregious, you oughtn't to ever shade that way.
You can see the obvious transition between colors on the leftmost image. There are techniques you can use to avoid that, such as dithering.
The wall and floor tiles are obvious and repetitive, and your light sources are conflicting. On all the vats we see a distinct light source coming in from the front-right, but all the wall tiles appear to be lit from directly in front, and the floor is lit from something above. It removes all depth from the scene and it makes the occupants appear to be floating in mid-air.
Also, there is no shadow at all cast by the monitor, the vats or the guy at the keyboard.
Your best solution to the lighting issues is to pick a direction (top-right, top-left) and shade everything using that as a rule. You can get by without having to make many changes to the vats or tubes if you fix the floor and walls.
all the wall tiles appear to be lit from directly in front
This is called pillow shading, it's bad and should be avoided in almost every case.
Above image is from:
http://ffhacktics.com/smf/index.php?topic=8624.0All the things I've covered are in the tutorial linked in the OP. It tells you about things to avoid when you're spriting.