Veja algumas sugestões de temas simples, porém bonitos para Wordpressque por serem simples e basicos podem fazer com o que o seu site carrega mais rapido e fique melhor para todos os leitores:

SimpleBlocks: http://wordpress.org/extend/themes/simpleblocks
Cooge: http://wordpress.org/extend/themes/coogee (esse tem uma caixa de pesquisa perfeita)
Mortagage: http://wordpress.org/extend/themes/mortgage
Blueprint Theme: http://wordpress.org/extend/themes/blueprint-theme
SimpleGreen: http://wordpress.org/extend/themes/simple-green
ColdBlue: http://webrevolutionary.com/coldblue/
Zindi: http://wordpress.org/extend/themes/zindi
Downtown Night: http://wordpress.org/extend/themes/downtown-night
Simple Write: http://wordpress.org/extend/themes/simple-white
Simple Blog Design: http://wordpress.org/extend/themes/simple-blog-design
Simplenotes: http://wordpress.org/extend/themes/simplenotes
TAHTsimple: http://wordpress.org/extend/themes/thatsimple