Inevitably, with the advent of cinema came the need to market films to audiences prior to release - it's just good business sense - and though the internet now exists to celebrate (and intentionally spoil) upcoming movies on the slate, some traditional marketing approaches still survive. Stoke the fires of imagination and throngs of cinemagoers shall hand over their hard-earned cash for entry into the latest feature doing the circuits.
Way back at the start of the last century, movie posters were only really permitted for use by the movie theatre owners and so designs were whipped up to convince folks to return to the cinema. An image, a headline and the name of the leading actors; these three assets were the bread and butter for early film poster designers, and thankfully, you'd see no horribly Photoshopped disaster, under-selling a movie that deserves so much better. Some of those classic movie posters have gone on to fetch millions at auction - not for the films own merit, but for the divine artwork dedicated to it.
But that would be unthinkable now, as in recent years posters have depreciated as they've been churned out more cynically (unless we're counting the limited run special edition posters that are released in small batches by terrific artists like Mondo). While there are undoubted exceptions to this, namely in foreign movie posters, the majority of mainstream posters now lean towards enticing customers by revealing a lot more of the plot than merely its title, a random image and the names of its stars.
Unfortunately, screenshots, multiple characters, and the tagline can often reveal far more than a glimpse at what's to come, and sometimes they can ruin the element of surprise completely, compromising the impact when the ultimate reveals eventually happen on screen.