There might not be any way to remove the "acorn" default icon / avatar.
You can turn off seeing everyone's avatar -
Profile
Change your site preferences
Show member avatars? - - - - NO
You can also disable seeing the animated jumping smileys / emoticons:
Show forum smilies and emoticons?
And social media doo-dads:
Show facebook and other social media widgets?
One handy field there is how many posts to show per "page":
Show how many items per page?
If you have a slow connection like dial-up, the number should be set low so you don;t have to wait to see the posts. If you have a fast connection, using a large number means less jumping around. I use "100" so I know how many posts there are in a thread with (say) 10 pages.
If this field does not default to "YES", you probably want to set it that way:
Automatically jump to the first unread post in threads? - - - - YES
