Should we provide better alternative for NFT collection icon if none is available?

When a token icon isn't available for download (i.e it's not in `iconassets`, `OpenSea` API and not in our fallback repo), we fall back to the image of the first token the user own. Do we want to provide a better alternative or is this good enough?

Screenshot after #3860 is applied, which supports pulling bigger images from `iconassets` repo for NFTs.