I have to create a 4-banner wide roll-up design, but all I have to work with is a 1500px wide image. If I resize this, so it fits the banners, it becomes, logically, very pixelated. I have taken a look at this question, but the result (after importing it in Illustrator) looks quite blurry.
This is why I'm wondering if there is a function or trick in Illustrator to blow up a picture, without it looking like crap. Of course it doesn't have to look like it's not resized, but it should be good enough to take pictures in front of.
The image I'm working with is this one.