Your wall is "dry-lined" as is mine and most new houses. Picture hooks should be fine, I've had some on mine for >10 years. I'm talking here about the ones where there is a strong pin which goes into the wall at an angle. Trying hang anything heavier on this type of wall can be a problem and normally you have to use long screws into the wall behind.
There's a huge variety of plasterboard fittings which cater for loads heavier than a picture but for which it's not worth doing the "must find studs" or "must extend into brickwork" dances. I've found the metal Redidrivas (relatively cheap in bulk at Screwfix, prodcode 11923) easy to use (can drive straight into wall without drilling, though a small (5mm) pilot hole helps make sure you have got a hollow bit rather than having accidentally found a stud or a plaster dab); I also have a fondness for the hollow wall anchors, 12229 or 11143 depending on wall thickness, but these are a tad more temperamental - a great fixing when the legs collapse as they should, a right PITA if (as I've had happen too often) the nut at the back just spins round and round, or the bolt jams and you end up tearing through the skim coat as the whole anchor then turns).
Try some out (maybe get a little pack from a corner ironmongers or a shed) and see which works best for your walls and personal taste...
HTH, Stefek
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