This guide is for people wondering how to edit certain sprites in B2/W2 like Trainer mugshots and Starter selection sprites. It also works for sprites in other DS games.
To get started, you need to download the latest version of Tinke, which can be found here.
Step 1. Open up Tinke and load the ROM you want to edit. I'll be using Pokemon Black 2 (U).
Step 2. The program will load with a directory of the ROM on the left side. Use this link to find where your sprite is located. I want to edit the mugshot of Nate, and mugshots are located in /a/2/6/7
Step 3. After you locate the narc where your sprite is, open it up using the Unpack button near the lower right corner.
Step 4. Unpacking this specific narc will reveal a bunch of bin files and a bunch of RLCN (palette) files.
Step 5. In order to view the sprite correctly, we need to select the correct palette file first. Nate's palette is near the bottom of the list at 7_72.RLCN. Select it, then press the View button, and you should get a box of 16 different colors.
Step 6. Now let's open Nate's mugshot. It's located at 7_47.bin. Unpack it, then click View, and you should see the sprite with the correct colors.
Step 7. Now you can save it to your computer as a PNG using the Export button on the lower right corner.
Step 8. Use your favorite graphics program to edit the sprite however you want. Do not resize the image and do not use more than 16 colors.
Here's an example of an edited mugshot:
The green background is the transparency color. Do not use this color in your actual sprite unless you want it to be transparent in the game.
Step 9. Save the sprite as a PNG and go to Tinke. Click on the Import button. If you are using different colors than the ones the sprite originally had, be sure the click the "Replace palette" option down at the Palette import options section.
Step 10. If your sprite imported correctly, Pack all the files you Unpacked, then click the Save ROM button. Wait for it to finish saving, then test out your edit using an emulator.
If everyone looks fine, then congrats, your edit was successful! With Tinke, you can edit pretty much any sprite in the game, including things like Prof. Juniper's intro sprite and even the sprites used during the credits. Sometimes you'll need to change the Offset/Width/Height of the sprite in order to view it correctly.
Sometimes you may find an image that looks like a sprite, but is actually a texture (usually ends in .BMD0). You can save these images, but I haven't figured out how to reinsert them or if that's even possible.
Anyways, hope this helps someone!