In the past, we've covered flowers, so this year I figured, why not a cake? At least it is edible! You can be super personal and make her a cake or if you are not at home, you can send her a cake. They have super convenient shops where you can order a cake online and have it delivered these days- just make sure you know where your mom will be on the day.....
A good idea, if I may say so myself, is night wear. Unless you REALLY REALLY know your mom, you will never find an item of clothing that she'd really like and would wear in public. So the next best thing is night wear. They are generally less picky about pajamas and robes since they are worn in the confines of home. You can even get them super cute matchey matchey ones (above: Victoria's Secret)! 
Or you can get her cute cushiony slippers (though Chinese superstition prevents me from giving anyone anything related to shoes...shame!) to walk around in or a set of luxury towels- hey, its practical, a home cannot ever have too many towels! (left: Victoria's Secret, right: Ralph Lauren).
More items for home. You can consider glass vases and bowls, like this very elegant Nambe Piroett bowl (left). Or there are essence like this Anthousa Blossom Ambiance Trio (right). I know, it doesn't sound very useful. But surprisingly, my mom actually uses it!! 
For something more personal, you may try getting them facial treatments. Not the daily ones since they probably already have a routine, but those intensive ones used once a week. My grandmother really really LOVES this intensive treatment one from Darphin (left) and if she loves it, it must be REALLY good. Or you can try the Estee Lauder intensive lifting mask above as well (right). I don't have any personal accounts about this product, but they are usually good with their rejuvenating products. 
And when all else fails, I always turn to Shutterfly- it is personalize but very easy and convenient. I quite like the canvas photo idea.Happy Mother's Day!
Image Source: Torrance Bakery, Shutterfly, Victoria's Secret, Ralph Lauren and Saks
