1. decrypt and dump rom
2. navigate to a/1/0/ and use GARCTool on file '3'
3. open ohana3DS and go to texture tab
4. drag and drop the bin file in the newly created '3_' folder
5. find image and hit extract
6. edit in photoshop or whatever (image has to be a power of 2 so theres extra pixels.. PC box images only show 220x210 pixels i think)
7. select image again in ohana and hit import
8. should look like this so far:
9. use GARCTool on 3_ folder to pack
10. clean up extra files and rebuild rom
11. ???
12. PROFIT
I didnt elaborate on step 1 and 10 because theres tutorials for that already and i wanted to make this short as possible, but also as newb friendly as possible.