The model and the name of the blend can be customized using a resource pack.
Blend Model
By default, all blends use the bland blend model. To change that, define a custom model at assets/<namespace>/models/blend_type/<blend_name>.json.
The simplest option is to create a 2D item model. Biome Blends provides a few blend textures that can be used:
bumpy_blendfluffy_blendrocky_blend
{"parent": "minecraft:item/generated","textures": {"layer0": "biomeblends:item/bumpy_blend"}}
Blend Color
You can apply a color tint to the blend's texture using a datapack.
Blend Translation
Each blend type requires a translation for its name, which has to be specified in assets/<namespace>/lang/en_us.json:
"blend_type.<namespace>.<blend_name>": "Blend Name"