That’s such a stunning Iwagumi - i especially love the use of Utricularia graminifolia as the front carpet - it creates the impression of movement and provides much more texture than Eleocharis acicularis Mini alone will
The use of those fish which reflect the colours of the manten stone, greatly enhance scape feel/vision
(And no ugly massive Amano shrimp 😀)
Mixing in various Eleocharis variants, or adding some (small amounts) Lilaeopsis may provide more texture, also when trimming, make sure to do this from the top down, angled, rather than horizontal cuts
This will also allow you to leave some longer grass stems through the carpet area - more like a natural meadow vs a nicely cut (& manicured) lawn
I’ve never managed to do a proper Iwagumi, I always get distracted into adding more plants ... which is something you can consider adding as the scape progresses (also small twigs reaching up through the grasses - though best to keep these easily removable for trimming sessions)
Blyxa is too heavy and dominating for my taste, so I’d not add any of this
There are some very delicate grassy looking Eriocaulons (if you have access to these species)
Junius repens can be used very sparingly for texture as well
When creating transitions between front carpet and taller grass background, use triangular or ragged edges, which will again contribute to the feeling of movement
Use of a point source light (Kessil, AI Prime style) and some (very) gentle surface agitation will enhance the textures/depth of the scape, stone shadows will also be more dynamic
(LEDs such as Twinstar, Aquasky etc produce a much flatter even appearance)