Open up "Title.bmp" in the data folder. By default, the game extracts the title screen a framerect in that image with the top-left corner of (0, 0), and a bottom right of (144, 40). You'll probably want to edit "Title.bmp" to have your full image in the top left region of the image, and change the bottom-right X/Y framerect values to 320/240, respectively. The "X Render Position" and "Y Render Position" defines where the title image will be drawn. For your purposes, I'm guessing you'll probably want to change these both to 0.
I'm guessing that the graphics for the "New" and "Load" buttons will need to be placed directly to the right, outside of wherever you set the framerect for the title screen.
Once you've changed those values accordingly, you should be able to patch in the hack by clicking "Commit!"