Mouth Morphemes
Large = ee
Thin, Small, Smooth = oo
Average = hmm
Long  = ahh
Sluggish = tongue out

Examples
The wall is huge. (ee) 
It has nice building sets. (oo) 
The skyscraper looks good. (hmm) 
There is a huge city of skyscrapers. (ahh) 
This house looks old. (tongue out)