ADD esse codigo no custome.css
.cAuthorPane_photo img{
max-width: 150px;
}
Depois Vá em Forums>>front>>topic>>postconainer e procure por:
<li class='cAuthorPane_photo'>
{template="userPhoto" app="core" group="global" params="$comment->author(), 'large', $comment->warningRef()"}
</li>
Substitua por esse \/
<li class='cAuthorPane_photo'>
{{if $comment->author()->pp_main_photo}}
<a href='{url="app=core&module=members&controller=profile&id={$comment->author()->member_id}-{$comment->author()->name}" seoTemplate="profile" seoTitle="$seoName"}' data-ipsHover data-ipsHover-target='{url="app=core&module=members&controller=profile&id={$comment->author()->member_id}-{$comment->author()->name}&do=hovercard" seoTemplate="profile" seoTitle="$seoName"}' title="{lang="view_user_profile" sprintf="$name"}">
<span class='ipsUserPhoto ipsUserPhoto_variable'>
<img src="{setting="base_url"}uploads/{$comment->author()->pp_main_photo}" />
</span>
</a>
{{else}}
<a href='{url="app=core&module=members&controller=profile&id={$comment->author()->member_id}-{$comment->author()->name}" seoTemplate="profile" seoTitle="$seoName"}' data-ipsHover data-ipsHover-target='{url="app=core&module=members&controller=profile&id={$comment->author()->member_id}-{$comment->author()->name}&do=hovercard" seoTemplate="profile" seoTitle="$seoName"}' title="{lang="view_user_profile" sprintf="$name"}">
<span class='ipsUserPhoto ipsUserPhoto_variable'>
<img src="<Path_to>/default_photo.png" />
</span>
</a>
{{endif}}
</li>
Leo Mapper's postagem in [Dúvida] Campos de Perfil was marked as the answer