Jw always tout how much attention they give to details when in comes to their imagery. They claim to research everything about it. The images in their study WT are also crafted very meticulously to convey hidden rules and guilt in the smallest details.
I wouldn't put it past them to select an image that resembles a cross on purpose. Most JW will never notice and otherwise it can be denied....and to (other) Christians the image will subconsciously make them feel more connected to the topic....
But there's a big gap between 'wouldn't put it past them' and 'I think they did'...