Yes, you're exactly right. You should use radio buttons for single
choice and checkboxes for multi choice. Android has built in widgets
for these, but if you're dead set on using custom images, the images
you've chosen look just fine.
I don't really have anything to suggest as to putting the buttons to the
right or left of the answer. I've always put them to the right, but
really I don't know why. I think I'm just used to seeing input fields
to the right of labels. But that might just be me.