How to Instatiate an empty spriteObject and be able to draw a image/sprite like you would in paint?

My Question is that I'm making a level editor like you would find in Little Big Planet but instead of it being in 3d in the style of 2d. My level Editor is completely in 3d with 3 sort layers for the editor to draw in(4 if you include the sky). But I can't seem to find any information/tutorials on drawing images/sprite like you would in paint or photoshop at runtime. I know you can draw 3d shapes/customs shapes via code/runtime when making 3d games but is there a way to draw images and of cause give it a collider too.

My Level Editor is not tile map based.

Thank You for your help :)