Of course, one thing that can make a game stand out is its graphics. I've seen numerous threads about how to change the title screen in VX, so I'm going to explain how along with how to incorporate other system graphics. The first thing you have to do is locate the Resource Manager.
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(Click to enlarge)
The box circled in red is the Resource Manager. Click on this and you'll see a list of files on the left and a list of materials on the right. Find the file that is named Graphics/System (VX) and click on it. The system graphics for RMXP have been further broken down into Graphics/Title, Graphics/Windowskin, etc., but it's the same thing except for where to find/place it. On the right, you'll see the list of graphics which are used throughout the game - the title screen, tilesets, windowskin, gameover screen, etc. To see what each one looks like, highlight the material and click Preview... on the right.
It's always good to click Export... on what you want to change, save it to your computer, and opening it with your editor before making a custom graphic so you have a template to work with. After you have the graphic, to include it to take the place of one of the default graphics, you'll need to rename the graphic to what is shown in the Resource Manager. For example, if you want a new title screen, you should name the file that you're going to use Title. This is essential for RMVX, but the file can be named differently in RMXP.
Once this is done, click on the import button when under Graphics/System and choose the file you've named. You'll notice that whichever graphic you replaced will be moved to the top on the right and the small circle next to it will change from blue to orange. If you click preview, you'll notice that it now displays your custom graphic. In RMXP, you need to go into the Database (icon to the left of Resource Manager), go into the System tab, and set the graphic in there. That's it! You've now replaced a system graphic with your own custom graphic! Of course, I recommend testing the game to make sure everything aligns as it should.