Yea, being able to add custom icons would be great.
One more thing. It seems that icons are not synced between devices, only the bookmark/speed dial itself is. This should be fixed 
Best posts made by micke88
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Opera for WindowsRE: [Solved]How to add Icons on Speed Dial
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Opera for Windows[Solved]How to add Icons on Speed Dial
What is required to get an icon on the Speed Dial? Some sites seem to get icons, but most don't. Even on my own sites I don't know how to set an icon. What does Opera look for? It does not seem to be the standard
favicon?