guys you don't need to open the gu, follow my steps
1)Download this
HERE
2)Extract the "3DS Banner Maker 2.0"folder
3)Create a .png in 256x128 size and rename it to"256x128" and move it to "3DS Banner Maker 2.0\cbmd_bannerImage" (this is the banner image)
4)Now run the "banner.py" inside"3DS Banner Maker 2.0\cbmd_bannerImage" folder
5)Create a .png in 48x48 size and rename it to "icon" and move it to "3DS Banner Maker 2.0\ctpk_48x48icon" (this is the homemenu large icon)
6)Now run the "icon.py" inside"3DS Banner Maker 2.0\ctpk_48x48icon" folder
7)Create a .png in 24x24 size and rename it to "icon" and move it to "3DS Banner Maker 2.0\ctpk_24x24icon" (this is the homemenu small icon)
8)Now run the "icon.py" inside"3DS Banner Maker 2.0\ctpk_24x24icon" folder
9)Open the "AppData.txt" in "3DS Banner Maker 2.0" folder and edit the "longtitle,shorttitle and publisher" and save it
10)Now run the "_buildscript.py" inside the "3DS Banner Maker 2.0" folder
11)Now you have "banner.bnr" and "icon.bnr" rename the "banner.bnr" to "banner.bin" and "icon.bnr" to "icon.bin"
i hope this help you guys!