Isn't a wave of presidential pardons in an administration's last days a bit suspicious?

Not as such.  Most outgoing presidents offer a raft of pardons when they leave.  But what's unusual is who is being pardoned.  When most Presidents leave office they pardon general American citizens who were convicted of crimes but who they thought might have been over-sentenced, or perhaps wrongly convicted.  Sometimes these pardons are saved for the end of their term because they might be politically controversial from a "tough on crime" standpoint.  What's highly unusual is to do what Trump is doing: offering pardons to people closely associated with him,  and ones who have committed crimes in relation to his political career.  The closest examples I can think of are Bill Clinton, who in his last day in office pardoned a major campaign donor (among several others) and George W Bush, who commuted the sentence of Scooter Libby a staffer for VP Dick Cheney who had been convicted in relation to a scheme where the Bush administration had public outed a CIA officer in order to punish her husband, a retired diplomat, for speaking out against the Iraq War.  Those were probably the most corrupt presidential pardon examples before Trump, at least in recent history. 

Every president does a lot of pardons in his final days.  Trump is kind of abusing the privilege (as he does with everything else.)  He's made it clear from the start that he wasn't going to be a president who was restricted by norms, traditions, customs.  Like civility, for instance.  Or hiring advisors and cabinet secretaries who know what they're doing.  Or accountability.  Or respecting the electoral process.  This is just one more thing.

Trump has not given a pardon to his immediate family yet == but it is coming.  And I think he will also pardon himself. 

it might be suspicious

Is there anybody left to pardon besides the big cheese himself?

No. President Trump is simply making right what was wrong. The left and their allies won't hesitate to set up, convict, and imprison. 

God Bless our President! 

Not to his voters. To them he is an angel sent by Christ himself to lead America out of the dark ages of Islam and Judaic secularism.