So with IPS the default avatar is small to say the least but it also must be square, which doesn't leave room for that awesome profile style that many a roleplayer loves. It is still possible but it takes a little extra work. Please note, that by doing this you must manually add each of your Profile field items to your authorPane otherwise this image will show twice.

First off, you need to create a Profile Field in Members > Member Settings > Profile For me I just named it "Big Avatar" and used the following settings:

The group does matter so if you intend to separate it out I recommend to do it now. But I chose not to show it on the profile, no real point to do that, but to show it in posts with the following code. This code will grab the file and add all necessary upload options to it.

<img src='{file="$content" extension="members"}' />

Next we need to edit your Post template. To do that go to Themes > Themes > Click on the < / > icon next to your theme. I certainly recommend this be a test theme to start.

In this first list you'll need to find postContainer. It is forums > front > topics > postContainer

Here you need to find this:

				{template="customFieldsDisplay" group="global" app="core" params="$comment->author()"}

Remove it. This removes the duplicate field bit.

Next you need to find this:

{template="userPhoto" app="core" group="global" params="$comment->author(), 'large', $comment->warningRef()"}

And replace with this. But there will be something you will have to replace with your own variables and I'll show you how after this section:

              {{if $comment->author()->contentProfileFields()[core_pfieldgroups_2][core_pfield_2] != ''}}
          		{$comment->author()->contentProfileFields()[core_pfieldgroups_2][core_pfield_2]|raw}
          	  {{else}}
				{template="userPhoto" app="core" group="global" params="$comment->author(), 'large', $comment->warningRef()"}
              {{endif}}

This is the bit you need to focus on:

[core_pfieldgroups_2][core_pfield_2]

This first part [core_pfieldgroups_2] is the profile field group or category. The latter part [core_pfield_2] is the profile field itself. So the easiest way to find this is to go to your Members > Member Settings > Profile and look at the URL when trying to edit these:

If that doesn't work go to the URL and copy and paste it into an editor or use your handy dandy inspect tool for each.

Once you've done that I recommend one last bit, since not all users know how to resize images. It's always best to add a little bit of preventive CSS to your custom.css:

.cAuthorPane_photo img {
  max-width: 250px;
  max-height: 400px;
}

This will guarantee that the avatar isn't over the size of 250px width and 400px height.

There is plenty more to expanding the author pane  but this will at least give you a little direction and possible help you create an awesome custom mini profile for your OOC accounts.