SharePoint 2013 How to remove default logo from Master Page
Open master page. Search for: siteIcon. Then remove below code.
<div id="siteIcon" class="ms-tableCell ms-verticalAlignTop">
<SharePoint:AjaxDelta id="DeltaSiteLogo" BlockElement="true" runat="server">
<SharePoint:SPSimpleSiteLink CssClass="ms-siteicon-a" runat="server" id="onetidProjectPropertyTitleGraphic">
<SharePoint:SiteLogoImage CssClass="ms-siteicon-img" name="onetidHeadbnnr0" id="onetidHeadbnnr2" LogoImageUrl="/_layouts/15/images/siteIcon.png?rev=31" runat="server" />
</SharePoint:SPSimpleSiteLink>
</SharePoint:AjaxDelta>
</div>
<SharePoint:AjaxDelta id="DeltaSiteLogo" BlockElement="true" runat="server">
<SharePoint:SPSimpleSiteLink CssClass="ms-siteicon-a" runat="server" id="onetidProjectPropertyTitleGraphic">
<SharePoint:SiteLogoImage CssClass="ms-siteicon-img" name="onetidHeadbnnr0" id="onetidHeadbnnr2" LogoImageUrl="/_layouts/15/images/siteIcon.png?rev=31" runat="server" />
</SharePoint:SPSimpleSiteLink>
</SharePoint:AjaxDelta>
</div>
