This is only an example.

How can I make images appear to float on the background like that?

Using Photoshop ofc

could you explain a little more please?

after you cut out the items and place them where you want, turn off the background you are using so it has a transparent background (should be white and grey checkered). Then, right-click the layer with the slices and go to Blending Option. One of the options on the left is Drop Shadow, that is the effect you want, check the box and go into that tab/menu to give it some adjustments to make it how you want and then save as a PNG.

tyvm

I did exactly as you guided me, but for some reason the background stays visible. I save it as a jpg after I'm done working on it in Photoshop and then upload it to imageshack. Here is one result of mine:

oh I missed that last sentence fml lol