Euphemisms are sayings that allow us to temper or soften harsh, awkward, uncomfortable, politically incorrect situations. Likely you have used an euphemism sometime during the day. Maybe you 'tooted' and not farted or you were 'busy' instead of saying you just can't stand to be in the company of your best friend. Essentially, we speak in euphemisms to be polite. In the phrase above, "Good Vibes Only" the euphemism is that this business doesn't want your negativity, your angst, or your bad mojo. Using the word 'vibes' connotes a chill surfer tone which plays great against the cold grey city concrete inviting not only your "good vibes" but also your wallet.
The importance of an oxymoron is that it provides opposition, mostly through humorous thought provoking phrases, to reflect life's conflicting duality. This image is oxymoronic because it portrays a "mechanical man." A mechanical man reflects humanity's reliance upon technology over reason. Or it could show that humanity is colder, more mechanical, thus disconnected from one another than ever before. Or the mechanical man represents citizens as in Orwell's 1984 where conformity rules and people will not risk their life to be an individual and different - they give themselves over to the power of Big Brother and the Thought Police.
Hyperboles are exaggerations of the extreme and while they are meant to be humorous, they can also be used to correct a social blunder or faux pas. They are not meant to be taken literally but promise to heighten a moment through amusement, emotions, or surprise. In the statement above, "I'm Killing Time", the dark humor suggests murder is an entertaining way to pass time while waiting for something else to do. Or, maybe like Macbeth, consumed with guilt over killing, you feel that there is not enough water in the ocean to wash the blood of your deed off of your hands: "Will all great Neptune’s ocean wash this blood / Clean from my hand? No. This my hand will rather /The multitudinous seas incarnadine, / Making the green one red."
What makes paradoxes so fun is that they must contain a contradiction, be true and untrue at the same time, and... illuminate a truth. Paradoxes reflect the dual nature of humans and that our thinking is not always black and white but complicated and often confused. Many of us are much like the picture above. Sometimes we must be blind in order to see. Meaning, we cannot always trust our vision for us to see - intuition or feeling can be better guides than our eyes. Or, we could say that we are strangers to ourselves. When we look at ourselves in a mirror, see a quick unexpected reflection, or are unable to recognize ourselves in a photo, we indeed feel like a stranger to the person we should know most closely.