Specifically, what poetic imagery dominates William Blake's poem, "The Tyger"?

The "Tyger" is the dominant image of the poem, and the language which Blake uses to describe the animal often connotes fire (e.g., "burning bright," "Burnt the fire of thine eyes," "dare seize the fire"), which in turn connotes passion and vitality. The color of the tiger also stands out in stark contrast to the darkness of "the night," so that the connotations of fire, vitality and passion are emphasized even more.
Later in the poem, in stanza four, there is industrial, machine imagery, such as "the hammer," "the chain," a "furnace" and "the anvil." The language is part of a metaphor where the speaker imagines that the tiger must have been created in the blistering heat of a furnace, and that it must have been the product of great force, hence the hammer and the anvil. The implication is that the tiger's color and the intensity of "the fire of (its) eyes" is such that it seems only possible that it emerged from such intense conditions.
There is also imagery throughout the poem linking to the creator who the speaker cannot imagine to be responsible for creating the tiger. The speaker wonders, incredulously, "What immortal hand or eye" can possibly have created something like this "burning bright" tiger. The hand of any such creator is referenced throughout the poem, and the personification in this instance allows the reader to appreciate how difficult it must have been for any creator to have handled the fire from which the tiger must have been formed. We can all remember or imagine what it feels like to be burned, and so when the speaker wonders, "What the hand, dare seize the fire?" we, the readers, can better understand why the speaker is so reluctant to believe that the tiger could have been created by any hand. Instead, as the speaker suggests, it seems more likely that the tiger must have been created in a furnace.

The poetic imagery in Blake’s poem “The Tyger” revolves around fire (“burning bright,” “what the hand dare seize the fire,” “in what furnace was thy brain”). In the context of this poem, the fire represents the creative fire in which the tiger itself was forged, as we can see in the references to the tools of a blacksmith and his likely creations: the “anvil,” “hammer” and “chains.” This poetic imagery forms part of an extended metaphor which lends cohesion to the whole poem: that of God as the “immortal hand or eye” who, as a heavenly blacksmith, forged the Tyger in his fires.
The “fearful symmetry” of the Tyger is contrasted to The Lamb, and the poet asks whether the two creatures could be the work of the same artist, as it were. The Lamb here refers to Jesus Christ, but the imagery of the lamb contrasts neatly with that of the tiger, the two animals apparently at opposite ends of the spectrum of ferocity. The question is, of course, rhetorical; Blake does not intend to challenge the idea that the same God makes all, but to emphasise the breadth and variation in his creation.