Instructions
Download Lunar Magic for your PC. Select "Run" from the dialogue box that pops up when the file mounts on your desktop and click "Install" to install the program.
Open Lunar Magic and select "Open" from the "File" menu. Open your "Super Mario World" ROM image.
Click on the castle icon in the main menu at the top of the window. Click "File" and select "Title Screen." Click on "Edit Title Screen."
Click on the title screen and press the "Delete" button. Click on the rock icon.
Select a letter from the box that pops up and right-click on it. Drag it to the empty title screen to the area you want it to be. Repeat the process until you have a complete title screen.
Select a palette from the "Edit/Palette" menu and click the F12 button. Click "Yes" to save your title screen to the ROM.