Imad will join the county club for five matches before departing for the Caribbean Premier League (CPL), beginning August 5 at St. Lucia.
Bangladesh’s most accomplished batsman across formats, Tamim helped his side reach their first ever ICC tournament semi-final in the ICC Champions Trophy 2017, scoring 293 runs at 73.25 and emerging as the third-highest run-getter of the tournament.
Kent coach Matt Walker said Neesham, who has two Test centuries to his name, would bring some balance to the team for the competition that runs from July 7 to September 2.
Shahid Afridi had previous stints with Hampshire in 2011 and 2016.
Grant Elliott's spell with Warwickshire will be his third in English cricket following stints with Surrey and Leicestershire.
New Zealand's Luke Ronchi is to replace Sharjeel Khan as one of Leicestershire's overseas players in English county cricket's Twenty20 Blast.
Pietersen was most recently involved in the PSL, largely staged in the UAE, but withdrew from the Quetta Gladiators side that lost last weekend's final because of security fears concerning the match being staged in Lahore.
"I really enjoyed my time at Worcester with a great bunch of lads and it was so frustrating for me to pick up that injury in the very first T20 game," said Santner.
Josh Cobb rounded off his season in style after a sparkling innings of 80 helped Northamptonshire beat Durham in the final at Edgbaston.
NatWest are also the sponsors of the domestic competition known as the NatWest T20 Blast tournament in England.