I know nothing about Megapixl but my images appear not to be there. I did searches for some of mine (comparing with a Dreamstime search in another tab, you can see that only a fraction of the DT collection is at Megapixl)
Apparently three years ago I found out about them from a post here and contacted DT to ask what was up. If you read their reply, I guess what I wrote just now means my view of things hasn't changed in three years 
My rant about Megapixl written before I did a search to see how long they'd been around, etc.:
"I had opted out of third party partnerships - because I don't want to share buyer money with multiple agencies - which I have to assume is why my work isn't there. However Megapixl
isn't a third party - it's Dreamstime itself.
DT's sales are so pitiful it probably doesn't matter either way, but wholly-owned sites are not the same as third party partnerships and shouldn't be governed by opt-out choices made for third parties. Does anyone else remember when 123rf tried to claim that Inmagine was a third party and that entitled them to an extra share of the buyer payment? They backed down after everyone fussed, but does anyone know if DT is taking a partnership cut from the buyer's price when there's a sale on Megapixl? You have to hope that this scammery wouldn't happen twice, but if there's no marking "
A mind is a terrible thing to waste
