1) Celeberrimorum pictorum tabulae pinacothecas orbis terrae implent.
Famous pictures of painters has filled World galleries.
I am not sure is "of painters’ needed.
2) Hannibal magno cum elephantorum numero et ingentibus militum copiis per loca asperrima et difficillima Alpes superavit et in Italiam pervenit.
Hanibal has conquered Alpes with great number of elephants and mighty crews of soldiers over harshest and most difficult places and crossed into Italy.
3) O Gai Iuli Caesar, propter effigiem Pompei, acerrimi inimici, cecidisti.
O Gaius Iulius Caesar, you fold near statue of Pompei, the toughest enemy.
4) Pulcherrimam et uberrimam Aegyptum Herodotus, scriptor rerum, donum Nili amnis appellavit.
The most beautiful and wealthiest Egypt Herodotus, historian, has called the gift of river Nile.
5) Vulcane, impiger deus deorumque faber, cellerima fulgura Iovi excudisti.
Vulcanus, tough god and forger of gods, you made fast lightnings to Jupiter.
I am really unsure how to translate “impiger deus deorumque faber”