An age old battle
There were few photographs or pictures of any kind in the flat. At first Mrs Hudson had chosen a few bland, uninspiring paintings of flowers to hang in the alcoves surrounding the fireplace. These were soon deemed boring and were found one morning mysteriously harpooned adrift the kitchen floor and in their place stood a half filled bookshelf. "Cultured vandals, how odd, you learn something new every day" Sherlock had grinned. He had long since believed that book space was more important than living space, and much more so than art space.
Mr Hudson soon learnt how to deal with his eccentricities, but the tired and recovering army doctor arrived, so ignorant in Sherlock's ways it was laughable. After a lengthy debate on his third night, during certain points of which it was uncertain whether there would be a fourth, Sherlock had conceded that photographs of family were permitted within 221B. To be honest he was baffled as to why anyone would want to remember their mothers, but apparently it was a common social requirement. These were the little tricks that John was keen to teach but that Sherlock had little interest in learning, however in return for his efforts john was taught that any photograph which unwittingly strayed beyond the threshold of his room would meet an untimely end. The culprit behind these random acts of violence, unsurprisingly, could never be proven guilty.
Sherlock himself could only lay claim to own one photograph, although when asked about it he would deny its existence. He was never fond of expressing sentiment and to confess he owned the picture might make some see him 'more human' as John would say
The photograph was small. It would have easily fit inside a wallet if he were inclined to show it off, rather than vehemently deny its existence at every opportunity. Despite his apparent hate for the image, the dog eared corners betrayed how often it had been pulled from its hiding place within a book and held. He had the habit of twirling it between his fingers as he concentrated on particularly hard cases that kept him up at night. These sessions left the edges of the card cracked, white wrinkles surfacing at the fringes of the portrait and it had become slightly distorted in shape as it became bowed at the centre and generally dishevelled in appearance.
When they were very young, Mycroft wasn't so much a complete prat with a power complex as a boring ten year old who couldn't deduce his way out of a paper bag. Although they had squabbled frequently they had been as close to friends as either of them could stand. The two young boys were frozen, slightly out of centre, to the left of the frame, arms extended towards each other, at the ends of which were two silver blurs. Each boy had painstakingly created a sword of a different style from which ever materials they could salvage. Each style of sword reflected the costume they wore. The eldest was garbed something which was reminiscent of a ninja, clad in black from head to toe, with only the slightest break of fabric at his eyes. His sword had been thin, deftly made to replicate the style of a samurai sword from paper and tin foil. The youngest wore an eye patch and a scruffy waistcoat over a striped t-shirt, he had also donned three quarter length trousers and a hat that was much too small for his head and made from paper which tried to balance amongst the mad black curls of his head. He traversed the patterned carpet bare foot, and a red scratch, which had been bestowed on him by an irritable cat, added to his rugged pirate image well, that and his cutlass, with its wide base, meandering blade and menacing point. He held the weapon as though very familiar with its balance, the boy had spent hours perfecting and practising with the blade in the hope of besting his brother in battle.
Sherlock had always fancied that the image represented his hopes for the future. Mycroft wanted the mystery and skills of deduction that Sherlock possessed, whilst all he yearned for was excitement and adventure. At the time he had not invented the title he would one day introduce him as and he did not know what the consulting detective about town would wear, so he had adopted the assorted and jumbled attire of a pirate.
That was one interpretation of the image, another might have just been that two brothers had been partaking in the age old battle; pirates vs. ninjas.