Sure, it's pretty easy. The simplest method is to clip the image with a copy of the cloud shape. Here are the steps:
- Select the cloud shape and duplicate it (Ctrl-D).
- The cloud copy will still be selected, so now select the image by holding Shift and clicking it.
- Go to Object menu, choose Clip -> Set.
That will get what you want. If you group the cloud and image, you can move them around and they'll stay in the same positions relative to each other so it still looks right. However, if you need to edit the cloud shape, the clipping won't line up any more. To fix it, select the image, go to Object -> Clip -> Release. Delete the copy cloud shape that appears and redo the clipping steps above.
If you think you'll do a lot of editing to the cloud, you can keep the image automatically clipped correctly by using a Clone of the cloud instead of a duplicate. So in step 1 from above, use Alt-D instead of Ctrl-D. Now when you edit the original cloud shape, the clipping shape changes and the image is still clipped correctly.
There's another nifty thing you can do with object clipping, but I'll put it in a separate post below. The steps above give you the basic method.