For example, create a Heart shape with some background in Photoshop or AI, but cut that heart shape to be transparent,
This is what I did in my example just above - created in Illustrator. But I guess I'm not understanding your request.
Here is another example (not mine) - this might be closer to what You want...
svg_mask_apple_logo.hype.zip (126.9 KB)
Original thread: Masking question - #2 by michelangelo
Just use an Illustrator (or whatever program) to create the heart and export as SVG - as You noted above.