You do not need photoshop exactly but it can be easier for some things.
*edit: For courts there may only be a Lagao template in the form of a .psd file. You would obviously need photoshop for that specific court template.
I have considered making a more accurate court template with the UV maps if I can find an alternative for the psd file so that layers can be included I will try to help with that (maybe pdn file)
Paint.NET is an alternative that I use when I don't want to wait for photoshop to load so I can make a minor edit.
https://www.getpaint.net/download.html#downloadPaint.NET dds plugin :
https://forums.getpaint.net/topic/11173 ... 018-06-03/There are plugins that allow for the new image compression formats but honestly the newest ones aren't necessary yet unless you are running max everything with a great computer probably.
GIMP
https://www.gimp.org/This got me started in 2K17 when I didn't have photoshop yet. I liked it much better than photoshop for a while until this year when I started using photoshop instead because of the new format.
For just starting out though GIMP is great. A lot of the games images are .dds so I think you need to have a plugin but once you get that figured out you can start shopping a lot of textures and changing a lot and make mods!
Also 7zip is a MUST for these .iff files. You will want to look into gregkwaste's NBA2K_Explorer if you haven't already
.iff files are essentially zip files. you can use 7zip to open the archives directly so you can drag n drop dds images or you can create a folder, zip it with 7zip then simply rename the extention from .zip to .iff