Challenge: Construct as many Kennings (Old English Poetry, for example in Beowulf, 'Oar-Steed' means Ship) for the following words, in their current form (Imperative); 'Compose', 'Seek', 'Dream' and 'Imagine'.

Remembering that kennings offer a visual or sensory description of a word's meaning, I can offer some suggestions for thinking about the words you list, but very much want to emphasize that these are simply to offer guidance: you need to use these as a starting point for developing your own kennings.
So let's think about what the command "compose" means: one meaning is to write something: what image comes into your mind when you think about composing or writing an essay or a poem? Do you think about paper and a pen? Do you think about words flowing in black ink across a white page? A kenning would involve this type of imagery. To compose could be to "page-ink." I am sure you can come up with other images. Could you think up an image that would picture composing on a computer?
Likewise, what does "seek" conjure in your mind: to search for something? To head out on an adventure? Is it searching for a treasure? Could you call it "treasure hunt?"
I will do a little bit more to give you the idea: remember, just think about what concrete pictures the word forms in your mind to create a kenning.
OK, "dream." What do you think about--what picture arises-- when you read the word dream? Ghostly images? Weird images? Could you call a dream a "weird-picture" or a "jumble picture?" Do the same for imagine. What visual picture comes into your mind when you think about the word? Do you think about how the world could be better, brighter, more colorful? Do you build castles in the clouds?How could that become a kenning?  When you imagine do you "Castle-paint?"  Again, I am sure you can come up with more and better ideas.