Favourite sites icons not showing up on homescreen

Hello,

I very recently moved from Chrome to Safari, and i immediately started adding sites to my favourites bar, changing my homescreen picture, etc. I've always been a person with a HUGE need to personalise and change anything that is mine, so i came across a small problem recently.

Turns out that when i added my favourite sites to the bookmarks section, the icons of each site showed up just fine:

However, whenever i open safari, my homescreen pops up with most of the icons displaying only letters, instead of the regular images:

I've tried refreshing the page, removing and re-adding the favourite sites, but nothing seems to work. Is there any way to make the actual images of each site show up instead of those letters just like in the favourites bar? Or even just be able to manually change the icon images for each bookmark?

This probably has already been asked before, but i thought i'd give it a shot. Thanks!