What you need is increased icon cache size
Registry:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer]
"MaxCachedIcons"="65535"
The value MaxCachedIcons is in KB. Default value is 500KB. I use many tabs with many icons thus my value is 64MB (65535). This is max possible value.
I use Start11 "folder as a tab" feature for easier tool link file management. Separate folders (and Start11 tabs) with Windows standard tools links, my programming tools links, administration tools links, etc.
Even with big icon cache size 64MB initial load take a few seconds. After that menu appears instatly. Sometimes menu is reloaded again despite no change in folders with links. I presume icon cache overflow, which triggers reload. I have no solution how to increase icon cache size beyond 64MB.
Any change in a folder with links triggers Start11 menu reload.