In the past couple of decades, advertisers have apparently reduced the use of embedded imagery. They discovered that by simply providing richly-textured visuals (for example the complexity of ice cubes in a glass with a drink), individuals tend to project their own fantasies into the imagery, much as when seeing pictures in clouds or visual white-noise. That is, the advertisers don't need to put "sex" in the ice cubes, the viewers do it for themselves! Or, more specifically, the rich textures are "evocative" i.e. evoke feelings directly, without need of being interpreted as specific imagery.
This in turn has much to do with the fact that the brain is optimised for pattern-seeking. Given any noisy stimulus, the brain will organize it into patterns as far as possible. This is also where much of the "backward track" stuff in audio recordings come from. Consider that people routinely have to recognize intelligible speech in noisy environments: at parties, or in poor cellphone audio, or distant radio stations, etc. The same capability lets you pull meaningful information out of a backward audio track.
However, the use of subliminal stimuli did occur at one time, and probably still does to a limited degree. I have a folder full of examples that are so blatant it's impossible to miss them. I would guess that if it's still being done, some of it is the work of graphics people who are doing it for their own amusement, rather than something that's being ordered from on high.
And of course, advertising still makes use of motivational analysis and other more conventional psychological tools. These can be surprisingly potent, as evidenced by brand preferences in social groupings, and the degree to which people follow fashion trends in all categories of consumer goods.
The key to effective advertising basically boils down to being able to associate an emotional state with a product. There are numerous ways to do this, some of which are entirely respectable, others less so.
