Original Post:
Is it against the forum rules to be talking about any of this? If it is, then I'll remove this thread and my necrobomb post teasing Trooper Decontamination texture swapped to Trooper Green.

If it isn't against the forum rules, then I would continue to kindly spread the love and see what other people can do with texture editing. Forgive me. Just boredz, and have never seen this kind of discussion before, is all...

OP2:
So... I've realized how annoying it is to dump textures due to them being everywhere in the game with different looking versions. So in return, I've finally dumped all of the characters' textures, all neat and organized to their best ones, which should now work on all levels. So no need to knock yourselves out because (finally, took me 3 days) here is a better tutorial video with all character textures included!
OP3:
Better Widescreen Fix with Custom Textures & AR/Gecko Codes:
Finally, I've found out myself on how to use custom textures and AR/Gecko codes with Swiss-GC widescreen fix! No more relying on broken widescreen, bruvs!

Here's widescreen fix tutorial for TS2:
Firstly, you need Swiss-GC Nighty Build:
www.gc-forever.com/forums/viewtopic.php?t=1375
Open the swiss_r330 folder → DOL → copy
swiss_r330.dol to your dolphin games folder.
→ rename swiss_r330.dol to .WIDESCREEN_HACK.dol
Now...
1. Go into Documents → Dolphin Emulator → Load → Textures.
2. Make a folder called
00000000. That means 8 zeros.
3. Copy your custom textures mod folder into the
00000000 folder.
4. Startup Dolphin. To enable AR/Gecko Codes, on Dolphin menu, right-click on
TimeSplitters 2 → Properties →
AR Codes and/or
Gecko Codes tab → close. Codes won't work with Swiss-GC if you don't do this for some odd reason.
5. Now from Dolphin upper right corner, go to Open → .WIDESCREEN_HACK.dol. Then from Dolphin go to file → Change Disc... → pick your game like TimeSplitters 2 → from Swiss-GC, press A to load TimeSplitters 2 → press A again → press X for Settings → Force Widescreen: Persp → Save & Exit → Press A to Start ‘n’ Play!
6. Lastly, to load custom textures, from Dolphin, go to Graphics → Advanced → ☑ Load Custom Textures.
4 Years Later… a Tutorial for Dolphin 5.0 – Better Widescreen Fix while using Custom Textures & AR/Gecko Codes
You'll need to grab Swiss-GC Nighty Build for a better widescreen fix. I recommend
swiss_r330.
Open the swiss_r330 folder → copy
swiss_r330.dol to your dolphin games folder.
Now..
1. Go into Documents → Dolphin Emulator → Load → Textures.
2. Make a folder called
00000000. That means 8 zeros.
3. Copy your custom textures mod folder into the
00000000 folder.
4. Startup Dolphin. Go to Graphics → Advanced → check
Prefetch Custom Textures and
Load Custom Textures under
Utility → Close.
5. To enable AR/Gecko Codes, right-click on
TimeSplitters 2 → Properties → checkmark the codes under the
AR Codes and/or
Gecko Codes tab → close.
6. Run
Timesplitters 2 with codes enabled, then exit the game right away. Codes won't work with Swiss-GC if you don't do this for some unknown reason.
7. Run
swiss_r330.dol in Dolphin. Go back to the Dolphin window and right-click on
TimeSplitters 2 → click on
Change Disc...
Then go back on the Swiss-GC window → press A to load
TimeSplitters 2 → press A again → press X for Settings → Force Widescreen: Persp → Save & Exit → Press A to Start ‘n’ Play!
Creating Custom Textures
To grab the textures on Dolphin, go to Graphics → Advanced → and checkmark
Dump Textures under
Utility. Be warned! Dumping may be an extremely tedious process. Every character has 2-3 versions of skin textures that certain levels like to rely on. Some textures look worse than others, and using those as a base is probably not your best shot when it comes to texture editing.
Here's a faster route if you don't want to go through hoops. Photo editing programs like Paint.NET or Photoshop will do.
Useful Tools to Reduce Custom Texture Load Times
oxipng v1.0.4
JPEG & PNG Stripper
Both of these tools help optimize PNG textures by shrinking their file byte size without any quality loss.
Drag ‘n’ drop all
custom textures onto the
oxipng.exe, and then drag ‘n’ drop them on the
Stripper.exe for even smaller file size.