Trimming "Tile" graphics or filling to limits

I have a repeatable tile graphic which I've imported as a floor texture. Is there any way inside roll 20 to either trim the square tile graphic into a triangle for rooms which don't have perfectly square edges or better is there a way to have it fill to the limits of a polygon (or set it as the fill when drawing it)?

You cannot trim graphics inside roll20 but you can put them underneath other elements.  You can also fill a polygon either while drawing it or afterwards by selecting the second color. If doing it afterwards use the select tool to select the art, then change the second color as desired. - Gauss

I understand how to fill a polygon but as far as I cant tell I can't fill it using a texture in my art library correct? In a perfect world I'd like to be able to draw a polygon, select black as the outline, and select my tile texture as the fill but if I understand you correctly this isn't possible which means I'll have to create a triangle tile outside of roll20 correct?

I apologize for misunderstanding. You are correct, you can only fill a polygon or shape with colors.  Yes, you would need to trim it outside of Roll20.  - Gauss