I really adore the textures. The sponge has a realistic texture and is not glossy - giving it a realistic appearance.
I'm not crazy about the opaque jellies (?) embedded in the icing; however, I find it unique from other rainbow cakes, with solid sprinkles on top instead, on deviantart.
There are some inconsistencies I can spot. The cake closer to the camera has more pink and larger sprinkles compared to the other one with more green and smaller sprinkles visible. I can see some edges where the icing is a little awkward on the cake at the back, but I prefer that over a perfectly smooth and flat icing. Those would look less distracting if the icing was more 'whipped'.
I imagine the position of the earring hooks (?) would limit swinging movements than if it was attached to the other end - but I love this because these would hurt less when I walk/run.
I have mixed feelings about the photography of this deviation. First of all I'd like to point out that I prefer this presentation over your "Rainbow cake earrings with purple fondant" [link] - where I feel the background pattern is competing with the earrings and not letting them take focus. The non-uniformity of this background - in terms of soft/clear focus and colors - is a little distracting since the cakes already have many things going on.
I think I would have chosen a plain background to emphasize the earrings more - like this deviation: [link]. Or at least make the background softer like the top parts of the photo.
One last thing I would really recommend is to put more description. I think other deviants would love to read about what materials and methods you applied.
I prefer the earring closer to the camera - but overall I think you put in a lot of effort and did an awesome job. If someone gave this to me I would wear it in a heartbeat! I think it would look awesome as a ring too.
Sorry for the long critique. I would like to give credits to 2 critique guides I used for this: [link], and [link]