Topic category: User side tutorials
This small guide is made to quickly and efficiently show you how to use Minecraft base textures instead of MCreator ones. There may be a better one out there, but I didn't find it.
As you may know MCreator has made original textures for right reasons, but it probably looks out of place if you say, made a ruby armor, and you'd hardly see yourself using those textures as an experienced modder.
Step 1: Find the minecraft textures
You can find those online, but the safest way is most likely to grab them directly from your game files (if you do possess it)
If you play under Java, it should be in "C:/Users/[your username]/AppData/Roaming" (AppData is an hidden folder, so you have to toggle showing them. There are different ways to do it depending on your version or operating system, but a quick search will tell you.
Once you're in the minecraft folder, select versions, then the version you want to take textures from (you might have to have played/downloaded it before though).
Finally, open (explore, do not extract) the Jar file with a Zip Tool such as WinRar. Go to Assets>Minecraft
There you are. You could also copy stuff like audios and structures but we'll focus on textures.
Step 2: Copy them
Go to the textures folder, select the type of texture you want to take from, and then find the one you need. Copy it outside of the ZIP/Jar file, and you're good.
Step 3: Edit them
Now you can use a software like Gimp, Photoshop or Paint.net to change the colors or other parts of the textures. Small reminder to change brightness or contrast if your textures become flat with the color changes.
Step 4: Enjoy!
You just got a Ruby Armor texture that looks like a real Minecraft armor! The next step would be to make it unique while keeping the style, and training is a good way to learn that.
What if I want the mod to be affected by texture packs that change the vanilla textures?
I don't think this is possible, unless an external mod allows you to do that, unless you exactly use the vanilla textures in your mod, in which case it would change both vanilla items and mod items that use said texture.
However, someone who knows the name of the textures could add new textures for them in a resource pack, in such a way that your mod textures are also changed by the pack. But it has to be added inside of the texture pack instead of the mod.
I recall some texture packs having textures for Aether mod so it's definitely possible.
In the end it's a matter of files and naming. You could have two files with same texture but if one is left.png and the other is right.png you'll have to create two respective images inside the texture pack in order to change both, even if you want to give the same texture to both.