I have both rectangle and oval tablecloths for my oval table. I use the rectangle ones moreso for sentimental reasons. I have an off-white one that was my grandmothers that we use when that family gathers. I also have one that is a blue Chinese dragon silk embroidered tablecloth that my S/DIL brought back from China when they lived and worked there. We use that when our immediate family is all gathered around the table (for good luck and happiness that all are together).

The oval cloths probably looks a little nicer, more tailored. If you do use a rectangle make sure it's not too oversize otherwise the corners can hang too low.

I have knotted the hanging corners of a rectangular cloth (sheet actually) on my (gigantic) oval table.

Thanks, y'all. hilltop, I had completely forgotten about a smallish cloth that DH brought me from China. It might be good on this table! Now where did I put it.....

I've done both, but I like the look of an oval cloth better. If you're using it to eat at, the rectangles can get dangerous if anyone gets tangled up with it moving the chairs in and out...dinner may end up on the floor!