Making a simple city with various areas, shops, and arenas with guns and weapons would be very popular amongst a wide array of Minecraft players. My server uses Crackshot, a gun plugin that allows you to kill players and mobs with deadly snowballs from an item(bullets). I'm always expanding on this idea for my server, but i'm just suggesting this to you right now Hope this was helpful.
Stick with McSkin3d. This is just an opinion, but I believe the majority of the skinners here on PMC use this editor and prefer it over the others. Google it.
I really like this style of shading and I think this is probably one of the most useful tools in McSkin3d. I know this is about dodging and burning, but the colors and idea are a bit too simplistic (just my opinion). Other than that, I love the details put into the skin. Great job, Brick.
I'd say this would be a great gaming laptop. I have an ASUS 500GB memory, 4GB ram for about $300. For this computer, I run about 60-100 fps on a normal, default, singleplayer game. Overall, a very smooth experience. On your part, that computer should run about a 170-200 fps. It should be able to record with FRAPS at around 50-70 fps. I hope this post was helpful..
Most of these problems are caused by Paint. Expanding on what BasicBrick said, you should find a reliable skin editor. I use SkinCraft for my Minecraft skins. You can try it out here: http://www.scumlabs.com/misc/minecraft-skin-editor/. Feel free to check out a few of my skins to see if you like the ending result of what you can get from this editor.