BERLIN, July 24 (Reuters) - German consumer sentiment is set to dip slightly going into August as households remain cautious about spending amid more pessimistic income expectations, a survey found on Friday. The consumer sentiment index, published by the Nuremberg Institute for Market Decisions and the GfK market research institute, fell to -29.6 points in August from a revised -29.3 points the month before. In contrast, analysts polled by Reuters had expected the index to rise slightly, to -28.5 points.