No, it is against the rules to claim two prompts for one piece. In other words, if you claim two prompts, two pieces need to be created. Obviously you can always use a second prompt as inspiration, but this will still leave the prompt open to be claimed by someone else, since each prompt will only be allowed to be claimed once for fic and once for art.
Also, keep in mind, each participant is only allowed to claim two prompts in all, unless when done with the two pieces, there are still claims left and the participant has enough time to create a third piece.