Hi, which icons, social media ? ... are you talking about photos or icons? Could you make a screenshot with red marks, what kind of icons are you talking about.
K2 has configuration options - Parametrs Icon - and Images Tab, change size for "Item Large image width (in px)" then Save changes! this is general settings, sometimes you have to change also in Category parametrs tab.
(!) Remember if you want to have smaller image crop the height your own using Graphic Tool!
ok, I changed these 2 parameters but nothing happened. Actually, as far I can see, there are general K2 parameters. What if I want to change the image size of a individual k2 item?
You can not change image size only for only one item, you have to change for selected K2 category . Edit category -> Item image options or Item view options - to choose other size
(!) Remember to clear Cache memory of CMS (!).
If this don't work, say exactly want do you want do to with those photos and I will try to help you online.