ShotOne a C-130 fatal accident occurred for the very reason you state. To assist in loading tall cargo, a pilot initially held the control column aft to improve clearance below the elevators. Then he decided to prop it in that position by jamming an NVG case in front of it - but forgot to remove it before take-off. As a result the aircraft stalled, killing 11 PoB plus 3 troops on the ground.
Surely trainee pilots are taught never to obstruct the controls with anything, nor place loose articles anywhere which could interfere with full and free movement of critical aircraft controls?
Some of the trash-hauling VC10 mob of the lesser squadron developed a habit of sticking their pens / pencils etc. in front of the radio selector box on the centre console. Presumably because when they used to fly in Blues, they had no pen pocket. Some still did when they changed to wearing flying clothing instead - if I found a pen / chinagraph / whatever on the centre console I would confiscate it! When one aircraft was prepared for a full air test, the engineering team told me that they'd found the remains of an RAF chinagraph amongst the TPI sensing microswitches underneath the control column. They also found a first class BOAC teaspoon under the cockpit floor of ZA141 which must have been there for ages as the aircraft had been sold to Gulf Air, flew for years with them, was then bought by the RAF, rebuilt by BAeS and flew as a VC10K2 for many years until the spoon was found!
Cabin crew were also taught never to pass food / drinks to pilots over the centre console, to avoid the risk of spillage - is it the same in the airlines?
I don't know whether civil A330s have the same OITs as fitted to Voyager, or simply sliding trays. If they don't have OITs, the sliding tray is quite a convenient place for loose papers etc. - but sound training, good flight deck discipline and proper SOPs should mitigate jammed control risk in nay aircraft without any need for visual reminders, cheap though some black and yellow hatching would be.
Flying an F-4 once, as I manoeuvred it a large part of the instrument panel surround came loose and fell out of position. I stopped what I was doing and advised that I would RTB. The pilot of the other aircraft queried this (typical of a flt cdr keen to gain hours for the boss's wall graph...), but I made the point that if the panel was loose, what else had been forgotten by whoever had been working on the jet.