I do not know that "The Clod and the Pebble" gives any real new insight into the meanings of "The Lamb" and "The Tyger" because I think I understood those the same way before I read "The Clod and the Pebble" as I did afterward.
But I do think that the poems have more or less the same theme. They all (if you take "The Tyger" and "The Lamb" together) are talking about the fact that there is both good and evil in the world. And they are talking about how God must have made both. And they are suggesting that maybe there is a place for both in God's plan.
I guess one thing that may have changed a bit is that I wonder how positively Blake is thinking of the lamb. I wonder if he is thinking that it is too soft just like the clod.
These poems by William Blake show the difficulty inherent in defining and conceiving of love. Each presents what amounts to a dialogue on love, and might be approached as such. By discussing the various ideas that the dual voices in the poem suggest, one can be drawn into a dialogue that centers on the various ways to define love, love for things, and love for creation.
In "The Clod and the Pebble," love is presented by the clod as altruistic. One can consider how the nature of a "clod of clay"—soft, malleable, and capable of enduring the crushing force of the cattle—suggests a willingness to reshape itself in order to "give another ease" and "build a Heaven in Hell’s despair." Conversely, the pebble—representing a hard, unchangeable element—instead will treat love as self-serving, and, in the process, "joys in another’s loss of ease." One might consider how the physical substance of each, felt beneath one’s bare feet, might create sensory images that describe two varying sensations of love.
The Lamb and The Tyger express the same convictions.