<?php
            $pc = new WP_Query('cat=17'); ?>
            <?php while ($pc->have_posts()) : $pc->the_post(); ?>
            <a href="<?php the_permalink ?>">
                <div class="ui segment">
                    <span class="ui bottom attached label"><?php the_title(); ?></span>
                    <?php if ( has_post_thumbnail() ) {
                        the_post_thumbnail();
                        } else { ?>
                        <img src="<?php echo bloginfo('template_url'); ?>/img/logo.png" alt="<?php the_title(); ?>" />
                        <?php } ?>
                </div>
            </a>
            <?php endwhile; ?>