Is there more textures i can use, such as wood, metal, etc?
Yes, just type in google e.g. metal texture if you want metal texture.
how do i make things transparent?
Add new material in Assets > Create > Material or select an existing one.
Change shader to Legacy Shaders > Transparent > Difusse, change in the Main Color alpha channel (slider with the letter A) for any value and (if you want) change the color.
You can also choose the texture you want.
That's how it looks in the game:
