salesforce-getIconName-from-sObjectName.apxc

    public static String getIconName(String sObjectName){
        String u;
        List<Schema.DescribeTabSetResult> tabSetDesc = Schema.describeTabs();
        List<Schema.DescribeTabResult> tabDesc = new List<Schema.DescribeTabResult>();
        List<Schema.DescribeIconResult> iconDesc = new List<Schema.DescribeIconResult>();

        for(Schema.DescribeTabSetResult tsr : tabSetDesc) { tabDesc.addAll(tsr.getTabs()); }

        for(Schema.DescribeTabResult tr : tabDesc) {
            if( sObjectName == tr.getSobjectName() ) {
                if( tr.isCustom() == true ) {
                    iconDesc.addAll(tr.getIcons());
                } else {
                    u = 'standard:' + sObjectName.toLowerCase();
                }
            }
        }
        for (Schema.DescribeIconResult ir : iconDesc) {
            if (ir.getContentType() == 'image/svg+xml'){
                u = 'custom:' + ir.getUrl().substringBetween('custom/','.svg').substringBefore('_');
                break;
            }
        }
        return u;
    }